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/lb.json

@@ -1,42 +1,20 @@
 {
-  "title": "Keess",
-  "description": "Bestellungsofwécklung a Bezuelung",
-  "session": {
-    "title": "Checkout-Sëtzung",
-    "expired": "Sëtzung ofgelaf",
-    "invalid": "Ongëlteg Sëtzung"
-  },
-  "shipping": {
-    "title": "Liwweradress",
-    "select_address": "Adress auswielen",
-    "add_new": "Nei Adress derbäisetzen",
-    "method": "Liwwermethod",
-    "select_method": "Liwwermethod auswielen",
-    "not_available": "Net verfügbar fir dës Adress"
-  },
-  "payment": {
-    "title": "Bezuelung",
-    "method": "Bezuelungsmethod",
-    "required": "Bezuelung erfuerderlech",
-    "failed": "Bezuelung feelgeschloen"
-  },
-  "order": {
-    "summary": "Bestelliwwersiicht",
-    "subtotal": "Zwëschesumm",
-    "shipping": "Liwwerung",
-    "tax": "MwSt.",
-    "total": "Gesamtsumm",
-    "place_order": "Bestellung opginn"
-  },
-  "validation": {
-    "empty_cart": "Kuerf ass eidel",
-    "invalid_address": "Ongëlteg Liwweradress",
-    "insufficient_inventory": "Net genuch Bestand"
-  },
-  "messages": {
+  "storefront": {
+    "welcome": "Wëllkomm an eisem Buttek",
+    "browse_products": "Produkter duerchsichen",
+    "add_to_cart": "An de Kuerf",
+    "buy_now": "Elo kafen",
+    "view_cart": "Kuerf kucken",
+    "checkout": "Bezuelen",
+    "continue_shopping": "Weider akafen",
+    "start_shopping": "Ufänken mat Akafen",
+    "empty_cart": "Äre Kuerf ass eidel",
+    "cart_total": "Kuerf Total",
+    "proceed_checkout": "Zur Bezuelung goen",
+    "payment": "Bezuelung",
+    "place_order": "Bestellung opgi",
     "order_placed": "Bestellung erfollegräich opginn",
-    "checkout_failed": "Checkout feelgeschloen",
-    "session_expired": "Är Sëtzung ass ofgelaf",
-    "inventory_error": "E puer Artikelen sinn net méi verfügbar"
+    "thank_you": "Merci fir Är Bestellung",
+    "order_confirmation": "Bestellungsbestätegung"
   }
 }