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/orders/services/invoice_service.py

@@ -19,9 +19,9 @@ from sqlalchemy import and_, func
 from sqlalchemy.orm import Session
 
 from app.exceptions import ValidationException
-from app.exceptions.invoice import (
-    InvoiceNotFoundException,
+from app.modules.orders.exceptions import (
     InvoiceSettingsNotFoundException,
+    InvoiceNotFoundException,
     OrderNotFoundException,
 )
 from app.modules.orders.models.invoice import (

app/modules/orders/services/order_inventory_service.py

@@ -13,12 +13,12 @@ All operations are logged to the inventory_transactions table for audit trail.
 import logging
 from sqlalchemy.orm import Session
 
-from app.exceptions import (
+from app.exceptions import ValidationException
+from app.modules.inventory.exceptions import (
     InsufficientInventoryException,
     InventoryNotFoundException,
-    OrderNotFoundException,
-    ValidationException,
 )
+from app.modules.orders.exceptions import OrderNotFoundException
 from app.modules.inventory.models.inventory import Inventory
 from app.modules.inventory.models.inventory_transaction import (
     InventoryTransaction,

app/modules/orders/services/order_item_exception_service.py

@@ -15,12 +15,12 @@ from datetime import UTC, datetime
 from sqlalchemy import and_, func, or_
 from sqlalchemy.orm import Session, joinedload
 
-from app.exceptions import (
+from app.modules.orders.exceptions import (
     ExceptionAlreadyResolvedException,
     InvalidProductForExceptionException,
-    OrderItemExceptionNotFoundException,
-    ProductNotFoundException,
 )
+from app.modules.catalog.exceptions import ProductNotFoundException
+from app.modules.orders.exceptions import OrderItemExceptionNotFoundException
 from app.modules.orders.models.order import Order, OrderItem
 from app.modules.orders.models.order_item_exception import OrderItemException
 from app.modules.catalog.models import Product

app/modules/orders/services/order_service.py

@@ -24,12 +24,10 @@ from typing import Any
 from sqlalchemy import and_, func, or_
 from sqlalchemy.orm import Session
 
-from app.exceptions import (
-    CustomerNotFoundException,
-    InsufficientInventoryException,
-    OrderNotFoundException,
-    ValidationException,
-)
+from app.exceptions import ValidationException
+from app.modules.customers.exceptions import CustomerNotFoundException
+from app.modules.inventory.exceptions import InsufficientInventoryException
+from app.modules.orders.exceptions import OrderNotFoundException
 from app.modules.customers.models.customer import Customer
 from app.modules.orders.models.order import Order, OrderItem
 from app.modules.orders.schemas.order import (
@@ -39,7 +37,7 @@ from app.modules.orders.schemas.order import (
     OrderItemCreate,
     OrderUpdate,
 )
-from app.services.subscription_service import (
+from app.modules.billing.services.subscription_service import (
     subscription_service,
     TierLimitExceededException,
 )
@@ -1293,7 +1291,7 @@ class OrderService:
         order_id: int,
     ) -> dict[str, Any]:
         """Get shipping label information for an order (admin only)."""
-        from app.services.admin_settings_service import admin_settings_service  # noqa: MOD-004
+        from app.modules.core.services.admin_settings_service import admin_settings_service  # noqa: MOD-004
 
         order = db.query(Order).filter(Order.id == order_id).first()