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/tenancy/routes/api/admin.py

@@ -10,6 +10,8 @@ Aggregates all admin tenancy routes:
 - /platforms/* - Platform management (super admin only)
 - /vendors/* - Vendor management
 - /vendor-domains/* - Vendor domain configuration
+- /modules/* - Platform module management
+- /module-config/* - Module configuration management
 
 The tenancy module owns identity and organizational hierarchy.
 """
@@ -23,6 +25,8 @@ from .admin_companies import admin_companies_router
 from .admin_platforms import admin_platforms_router
 from .admin_vendors import admin_vendors_router
 from .admin_vendor_domains import admin_vendor_domains_router
+from .admin_modules import router as admin_modules_router
+from .admin_module_config import router as admin_module_config_router
 
 admin_router = APIRouter()
 
@@ -34,3 +38,5 @@ admin_router.include_router(admin_companies_router, tags=["admin-companies"])
 admin_router.include_router(admin_platforms_router, tags=["admin-platforms"])
 admin_router.include_router(admin_vendors_router, tags=["admin-vendors"])
 admin_router.include_router(admin_vendor_domains_router, tags=["admin-vendor-domains"])
+admin_router.include_router(admin_modules_router, tags=["admin-modules"])
+admin_router.include_router(admin_module_config_router, tags=["admin-module-config"])