refactor: complete module-driven architecture migration

This commit completes the migration to a fully module-driven architecture:

## Models Migration
- Moved all domain models from models/database/ to their respective modules:
  - tenancy: User, Admin, Vendor, Company, Platform, VendorDomain, etc.
  - cms: MediaFile, VendorTheme
  - messaging: Email, VendorEmailSettings, VendorEmailTemplate
  - core: AdminMenuConfig
- models/database/ now only contains Base and TimestampMixin (infrastructure)

## Schemas Migration
- Moved all domain schemas from models/schema/ to their respective modules:
  - tenancy: company, vendor, admin, team, vendor_domain
  - cms: media, image, vendor_theme
  - messaging: email
- models/schema/ now only contains base.py and auth.py (infrastructure)

## Routes Migration
- Moved admin routes from app/api/v1/admin/ to modules:
  - menu_config.py -> core module
  - modules.py -> tenancy module
  - module_config.py -> tenancy module
- app/api/v1/admin/ now only aggregates auto-discovered module routes

## Menu System
- Implemented module-driven menu system with MenuDiscoveryService
- Extended FrontendType enum: PLATFORM, ADMIN, VENDOR, STOREFRONT
- Added MenuItemDefinition and MenuSectionDefinition dataclasses
- Each module now defines its own menu items in definition.py
- MenuService integrates with MenuDiscoveryService for template rendering

## Documentation
- Updated docs/architecture/models-structure.md
- Updated docs/architecture/menu-management.md
- Updated architecture validation rules for new exceptions

## Architecture Validation
- Updated MOD-019 rule to allow base.py in models/schema/
- Created core module exceptions.py and schemas/ directory
- All validation errors resolved (only warnings remain)

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

app/modules/checkout/locales/en.json

@@ -1,42 +1,20 @@
 {
-  "title": "Checkout",
-  "description": "Order checkout and payment processing",
-  "session": {
-    "title": "Checkout Session",
-    "expired": "Session expired",
-    "invalid": "Invalid session"
-  },
-  "shipping": {
-    "title": "Shipping Address",
-    "select_address": "Select Address",
-    "add_new": "Add New Address",
-    "method": "Shipping Method",
-    "select_method": "Select Shipping Method",
-    "not_available": "Not available for this address"
-  },
-  "payment": {
-    "title": "Payment",
-    "method": "Payment Method",
-    "required": "Payment required",
-    "failed": "Payment failed"
-  },
-  "order": {
-    "summary": "Order Summary",
-    "subtotal": "Subtotal",
-    "shipping": "Shipping",
-    "tax": "Tax",
-    "total": "Total",
-    "place_order": "Place Order"
-  },
-  "validation": {
-    "empty_cart": "Cart is empty",
-    "invalid_address": "Invalid shipping address",
-    "insufficient_inventory": "Insufficient inventory"
-  },
-  "messages": {
-    "order_placed": "Order placed successfully",
-    "checkout_failed": "Checkout failed",
-    "session_expired": "Your session has expired",
-    "inventory_error": "Some items are no longer available"
+  "storefront": {
+    "welcome": "Welcome to our store",
+    "browse_products": "Browse Products",
+    "add_to_cart": "Add to Cart",
+    "buy_now": "Buy Now",
+    "view_cart": "View Cart",
+    "checkout": "Checkout",
+    "continue_shopping": "Continue Shopping",
+    "start_shopping": "Start Shopping",
+    "empty_cart": "Your cart is empty",
+    "cart_total": "Cart Total",
+    "proceed_checkout": "Proceed to Checkout",
+    "payment": "Payment",
+    "place_order": "Place Order",
+    "order_placed": "Order Placed Successfully",
+    "thank_you": "Thank you for your order",
+    "order_confirmation": "Order Confirmation"
   }
 }