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/de.json

@@ -1,42 +1,20 @@
 {
-  "title": "Kasse",
-  "description": "Bestellabwicklung und Zahlungsabwicklung",
-  "session": {
-    "title": "Checkout-Sitzung",
-    "expired": "Sitzung abgelaufen",
-    "invalid": "Ungültige Sitzung"
-  },
-  "shipping": {
-    "title": "Lieferadresse",
-    "select_address": "Adresse auswählen",
-    "add_new": "Neue Adresse hinzufügen",
-    "method": "Versandart",
-    "select_method": "Versandart auswählen",
-    "not_available": "Für diese Adresse nicht verfügbar"
-  },
-  "payment": {
-    "title": "Zahlung",
-    "method": "Zahlungsmethode",
-    "required": "Zahlung erforderlich",
-    "failed": "Zahlung fehlgeschlagen"
-  },
-  "order": {
-    "summary": "Bestellübersicht",
-    "subtotal": "Zwischensumme",
-    "shipping": "Versand",
-    "tax": "MwSt.",
-    "total": "Gesamtsumme",
-    "place_order": "Bestellung aufgeben"
-  },
-  "validation": {
-    "empty_cart": "Warenkorb ist leer",
-    "invalid_address": "Ungültige Lieferadresse",
-    "insufficient_inventory": "Unzureichender Bestand"
-  },
-  "messages": {
+  "storefront": {
+    "welcome": "Willkommen in unserem Shop",
+    "browse_products": "Produkte durchstöbern",
+    "add_to_cart": "In den Warenkorb",
+    "buy_now": "Jetzt kaufen",
+    "view_cart": "Warenkorb ansehen",
+    "checkout": "Zur Kasse",
+    "continue_shopping": "Weiter einkaufen",
+    "start_shopping": "Einkaufen starten",
+    "empty_cart": "Ihr Warenkorb ist leer",
+    "cart_total": "Warenkorbsumme",
+    "proceed_checkout": "Zur Kasse gehen",
+    "payment": "Zahlung",
+    "place_order": "Bestellung aufgeben",
     "order_placed": "Bestellung erfolgreich aufgegeben",
-    "checkout_failed": "Checkout fehlgeschlagen",
-    "session_expired": "Ihre Sitzung ist abgelaufen",
-    "inventory_error": "Einige Artikel sind nicht mehr verfügbar"
+    "thank_you": "Vielen Dank für Ihre Bestellung",
+    "order_confirmation": "Bestellbestätigung"
   }
 }