refactor: migrate templates and static files to self-contained modules

Templates Migration:
- Migrate admin templates to modules (tenancy, billing, monitoring, marketplace, etc.)
- Migrate vendor templates to modules (tenancy, billing, orders, messaging, etc.)
- Migrate storefront templates to modules (catalog, customers, orders, cart, checkout, cms)
- Migrate public templates to modules (billing, marketplace, cms)
- Keep shared templates in app/templates/ (base.html, errors/, partials/, macros/)
- Migrate letzshop partials to marketplace module

Static Files Migration:
- Migrate admin JS to modules: tenancy (23 files), core (5 files), monitoring (1 file)
- Migrate vendor JS to modules: tenancy (4 files), core (2 files)
- Migrate shared JS: vendor-selector.js to core, media-picker.js to cms
- Migrate storefront JS: storefront-layout.js to core
- Keep framework JS in static/ (api-client, utils, money, icons, log-config, lib/)
- Update all template references to use module_static paths

Naming Consistency:
- Rename static/platform/ to static/public/
- Rename app/templates/platform/ to app/templates/public/
- Update all extends and static references

Documentation:
- Update module-system.md with shared templates documentation
- Update frontend-structure.md with new module JS organization

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/cart/exceptions.py

@@ -2,7 +2,10 @@
 """
 Cart module exceptions.
 
-Module-specific exceptions for shopping cart operations.
+This module provides exception classes for cart operations including:
+- Cart item management
+- Quantity validation
+- Inventory checks
 """
 
 from app.exceptions.base import (
@@ -11,6 +14,15 @@ from app.exceptions.base import (
     ValidationException,
 )
 
+__all__ = [
+    "CartItemNotFoundException",
+    "EmptyCartException",
+    "CartValidationException",
+    "InsufficientInventoryForCartException",
+    "InvalidCartQuantityException",
+    "ProductNotAvailableForCartException",
+]
+
 
 class CartItemNotFoundException(ResourceNotFoundException):
     """Raised when a cart item is not found."""
@@ -115,11 +127,3 @@ class ProductNotAvailableForCartException(BusinessLogicException):
         )
 
 
-__all__ = [
-    "CartItemNotFoundException",
-    "CartValidationException",
-    "EmptyCartException",
-    "InsufficientInventoryForCartException",
-    "InvalidCartQuantityException",
-    "ProductNotAvailableForCartException",
-]

app/modules/cart/routes/pages/__init__.py

@@ -0,0 +1,2 @@
+# app/modules/cart/routes/pages/__init__.py
+"""Cart module page routes."""

app/modules/cart/routes/pages/storefront.py

@@ -0,0 +1,46 @@
+# app/modules/cart/routes/pages/storefront.py
+"""
+Cart Storefront Page Routes (HTML rendering).
+
+Storefront (customer shop) pages for shopping cart:
+- Cart page
+"""
+
+import logging
+
+from fastapi import APIRouter, Depends, Request
+from fastapi.responses import HTMLResponse
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_db
+from app.modules.core.utils.page_context import get_storefront_context
+from app.templates_config import templates
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter()
+
+
+# ============================================================================
+# SHOPPING CART
+# ============================================================================
+
+
+@router.get("/cart", response_class=HTMLResponse, include_in_schema=False)
+async def shop_cart_page(request: Request, db: Session = Depends(get_db)):
+    """
+    Render shopping cart page.
+    Shows cart items and allows quantity updates.
+    """
+    logger.debug(
+        "[STOREFRONT] shop_cart_page REACHED",
+        extra={
+            "path": request.url.path,
+            "vendor": getattr(request.state, "vendor", "NOT SET"),
+            "context": getattr(request.state, "context_type", "NOT SET"),
+        },
+    )
+
+    return templates.TemplateResponse(
+        "cart/storefront/cart.html", get_storefront_context(request, db=db)
+    )

app/modules/cart/services/cart_service.py

@@ -16,12 +16,12 @@ import logging
 from sqlalchemy import and_
 from sqlalchemy.orm import Session
 
-from app.exceptions import (
+from app.modules.cart.exceptions import (
     CartItemNotFoundException,
     InsufficientInventoryForCartException,
     InvalidCartQuantityException,
-    ProductNotFoundException,
 )
+from app.modules.catalog.exceptions import ProductNotFoundException
 from app.utils.money import cents_to_euros
 from app.modules.cart.models.cart import CartItem
 from app.modules.catalog.models import Product

app/modules/cart/templates/cart/storefront/cart.html

@@ -0,0 +1,319 @@
+{# app/templates/storefront/cart.html #}
+{% extends "storefront/base.html" %}
+
+{% block title %}Shopping Cart{% endblock %}
+
+{# Alpine.js component #}
+{% block alpine_data %}shoppingCart(){% endblock %}
+
+{% block content %}
+<div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
+
+    {# Breadcrumbs #}
+    <div class="breadcrumb mb-6">
+        <a href="{{ base_url }}" class="hover:text-primary">Home</a>
+        <span>/</span>
+        <a href="{{ base_url }}shop/products" class="hover:text-primary">Products</a>
+        <span>/</span>
+        <span class="text-gray-900 dark:text-gray-200 font-medium">Cart</span>
+    </div>
+
+    {# Page Header #}
+    <div class="mb-8">
+        <h1 class="text-3xl md:text-4xl font-bold text-gray-800 dark:text-gray-200 mb-2">
+            Shopping Cart
+        </h1>
+    </div>
+
+    {# Loading State #}
+    <div x-show="loading && items.length === 0" class="flex justify-center items-center py-12">
+        <div class="spinner"></div>
+    </div>
+
+    {# Empty Cart #}
+    <div x-show="!loading && items.length === 0" class="text-center py-12 bg-white dark:bg-gray-800 rounded-lg border-2 border-dashed border-gray-300 dark:border-gray-600">
+        <div class="text-6xl mb-4">🛒</div>
+        <h3 class="text-2xl font-semibold text-gray-700 dark:text-gray-200 mb-2">
+            Your cart is empty
+        </h3>
+        <p class="text-gray-600 dark:text-gray-400 mb-6">
+            Add some products to get started!
+        </p>
+        <a href="{{ base_url }}shop/products" class="inline-block px-6 py-3 bg-primary text-white rounded-lg hover:bg-primary-dark transition-colors">
+            Browse Products
+        </a>
+    </div>
+
+    {# Cart Items #}
+    <div x-show="items.length > 0" class="grid grid-cols-1 lg:grid-cols-3 gap-8">
+
+        {# Cart Items List #}
+        <div class="lg:col-span-2 space-y-4">
+            <template x-for="item in items" :key="item.product_id">
+                <div class="bg-white dark:bg-gray-800 rounded-lg shadow-sm p-6">
+                    <div class="flex gap-6">
+                        {# Item Image #}
+                        <div class="flex-shrink-0">
+                            <img
+                                :src="item.image_url || '/static/shop/img/placeholder.svg'"
+                                @error="$el.src = '/static/shop/img/placeholder.svg'"
+                                :alt="item.name"
+                                class="w-24 h-24 object-cover rounded-lg"
+                            >
+                        </div>
+
+                        {# Item Details #}
+                        <div class="flex-1">
+                            <h3 class="text-lg font-semibold text-gray-800 dark:text-gray-200 mb-1" x-text="item.name"></h3>
+                            <p class="text-sm text-gray-500 dark:text-gray-400 mb-2" x-text="'SKU: ' + item.sku"></p>
+                            <p class="text-xl font-bold text-primary mb-4">
+                                €<span x-text="parseFloat(item.price).toFixed(2)"></span>
+                            </p>
+
+                            {# Quantity Controls #}
+                            {# noqa: FE-008 - Custom quantity stepper with async updateQuantity() per-item and :value binding #}
+                            <div class="flex items-center gap-4">
+                                <div class="flex items-center gap-2">
+                                    <button
+                                        @click="updateQuantity(item.product_id, item.quantity - 1)"
+                                        :disabled="item.quantity <= 1 || updating"
+                                        class="w-8 h-8 flex items-center justify-center border-2 border-gray-300 dark:border-gray-600 rounded hover:bg-gray-100 dark:hover:bg-gray-700 disabled:opacity-50 disabled:cursor-not-allowed"
+                                    >
+                                        −
+                                    </button>
+                                    <input
+                                        type="number"
+                                        :value="item.quantity"
+                                        @change="updateQuantity(item.product_id, $event.target.value)"
+                                        min="1"
+                                        max="99"
+                                        :disabled="updating"
+                                        class="w-16 text-center px-2 py-1 border-2 border-gray-300 dark:border-gray-600 rounded font-semibold dark:bg-gray-700 dark:text-white"
+                                    >
+                                    <button
+                                        @click="updateQuantity(item.product_id, item.quantity + 1)"
+                                        :disabled="updating"
+                                        class="w-8 h-8 flex items-center justify-center border-2 border-gray-300 dark:border-gray-600 rounded hover:bg-gray-100 dark:hover:bg-gray-700 disabled:opacity-50 disabled:cursor-not-allowed"
+                                    >
+                                        +
+                                    </button>
+                                </div>
+
+                                <div class="flex-1 text-right">
+                                    <p class="text-sm text-gray-500 dark:text-gray-400">Subtotal</p>
+                                    <p class="text-xl font-bold text-gray-800 dark:text-gray-200">
+                                        €<span x-text="(parseFloat(item.price) * item.quantity).toFixed(2)"></span>
+                                    </p>
+                                </div>
+
+                                <button
+                                    @click="removeItem(item.product_id)"
+                                    :disabled="updating"
+                                    class="w-10 h-10 flex items-center justify-center border border-gray-300 dark:border-gray-600 rounded hover:bg-red-600 hover:border-red-600 hover:text-white transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+                                    title="Remove from cart"
+                                >
+                                    🗑️
+                                </button>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+            </template>
+        </div>
+
+        {# Cart Summary #}
+        <div class="lg:col-span-1">
+            <div class="bg-white dark:bg-gray-800 rounded-lg shadow-sm p-6 sticky top-4">
+                <h3 class="text-xl font-semibold mb-6 pb-4 border-b-2 border-gray-200 dark:border-gray-700">
+                    Order Summary
+                </h3>
+
+                <div class="space-y-3 mb-6">
+                    <div class="flex justify-between">
+                        <span class="text-gray-600 dark:text-gray-400">Subtotal (<span x-text="totalItems"></span> items):</span>
+                        <span class="font-semibold">€<span x-text="subtotal.toFixed(2)"></span></span>
+                    </div>
+
+                    <div class="flex justify-between">
+                        <span class="text-gray-600 dark:text-gray-400">Shipping:</span>
+                        <span class="font-semibold" x-text="shipping > 0 ? '€' + shipping.toFixed(2) : 'FREE'"></span>
+                    </div>
+
+                    <div class="flex justify-between text-lg font-bold pt-3 border-t-2 border-gray-200 dark:border-gray-700">
+                        <span>Total:</span>
+                        <span class="text-primary text-2xl">€<span x-text="total.toFixed(2)"></span></span>
+                    </div>
+                </div>
+
+                <button
+                    @click="proceedToCheckout()"
+                    :disabled="updating || items.length === 0"
+                    class="w-full px-6 py-3 bg-primary text-white rounded-lg font-semibold hover:bg-primary-dark transition-colors disabled:opacity-50 disabled:cursor-not-allowed mb-3"
+                >
+                    Proceed to Checkout
+                </button>
+
+                <a href="{{ base_url }}shop/products" class="block w-full px-6 py-3 text-center border-2 border-gray-300 dark:border-gray-600 rounded-lg hover:bg-gray-100 dark:hover:bg-gray-700 transition-colors">
+                    Continue Shopping
+                </a>
+
+                <p class="text-xs text-gray-500 dark:text-gray-400 mt-4 text-center">
+                    Free shipping on orders over €50
+                </p>
+            </div>
+        </div>
+    </div>
+
+</div>
+{% endblock %}
+
+{% block extra_scripts %}
+<script>
+document.addEventListener('alpine:init', () => {
+    Alpine.data('shoppingCart', () => {
+        const baseData = shopLayoutData();
+
+        return {
+            ...baseData,
+
+            items: [],
+            loading: false,
+            updating: false,
+
+            // Computed properties
+            get totalItems() {
+                return this.items.reduce((sum, item) => sum + item.quantity, 0);
+            },
+
+            get subtotal() {
+                return this.items.reduce((sum, item) =>
+                    sum + (parseFloat(item.price) * item.quantity), 0
+                );
+            },
+
+            get shipping() {
+                // Free shipping over €50
+                return this.subtotal >= 50 ? 0 : 5.99;
+            },
+
+            get total() {
+                return this.subtotal + this.shipping;
+            },
+
+            // Initialize
+            async init() {
+                console.log('[SHOP] Cart page initializing...');
+
+                // Call parent init to set up sessionId
+                if (baseData.init) {
+                    baseData.init.call(this);
+                }
+
+                await this.loadCart();
+            },
+
+        // Load cart from API
+        async loadCart() {
+            this.loading = true;
+
+            try {
+                console.log(`[SHOP] Loading cart for session ${this.sessionId}...`);
+                const response = await fetch(`/api/v1/shop/cart/${this.sessionId}`);
+
+                if (response.ok) {
+                    const data = await response.json();
+                    this.items = data.items || [];
+                    this.cartCount = this.totalItems;
+                    console.log('[SHOP] Cart loaded:', this.items.length, 'items');
+                }
+            } catch (error) {
+                console.error('[SHOP] Failed to load cart:', error);
+                this.showToast('Failed to load cart', 'error');
+            } finally {
+                this.loading = false;
+            }
+        },
+
+        // Update item quantity
+        async updateQuantity(productId, newQuantity) {
+            newQuantity = parseInt(newQuantity);
+
+            if (newQuantity < 1 || newQuantity > 99) return;
+
+            this.updating = true;
+
+            try {
+                console.log('[SHOP] Updating quantity:', productId, newQuantity);
+                const response = await fetch(
+                    `/api/v1/shop/cart/${this.sessionId}/items/${productId}`,
+                    {
+                        method: 'PUT',
+                        headers: {
+                            'Content-Type': 'application/json'
+                        },
+                        body: JSON.stringify({ quantity: newQuantity })
+                    }
+                );
+
+                if (response.ok) {
+                    await this.loadCart();
+                    this.showToast('Quantity updated', 'success');
+                } else {
+                    throw new Error('Failed to update quantity');
+                }
+            } catch (error) {
+                console.error('[SHOP] Update quantity error:', error);
+                this.showToast('Failed to update quantity', 'error');
+            } finally {
+                this.updating = false;
+            }
+        },
+
+        // Remove item from cart
+        async removeItem(productId) {
+            if (!confirm('Remove this item from your cart?')) {
+                return;
+            }
+
+            this.updating = true;
+
+            try {
+                console.log('[SHOP] Removing item:', productId);
+                const response = await fetch(
+                    `/api/v1/shop/cart/${this.sessionId}/items/${productId}`,
+                    {
+                        method: 'DELETE'
+                    }
+                );
+
+                if (response.ok) {
+                    await this.loadCart();
+                    this.showToast('Item removed from cart', 'success');
+                } else {
+                    throw new Error('Failed to remove item');
+                }
+            } catch (error) {
+                console.error('[SHOP] Remove item error:', error);
+                this.showToast('Failed to remove item', 'error');
+            } finally {
+                this.updating = false;
+            }
+        },
+
+        // Proceed to checkout
+        proceedToCheckout() {
+            // Check if customer is logged in
+            const token = localStorage.getItem('customer_token');
+
+            if (!token) {
+                // Redirect to login with return URL
+                window.location.href = '{{ base_url }}shop/account/login?return={{ base_url }}shop/checkout';
+            } else {
+                window.location.href = '{{ base_url }}shop/checkout';
+            }
+        }
+        };
+    });
+});
+</script>
+{% endblock %}