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>

middleware/auth.py

@@ -35,7 +35,7 @@ from app.modules.tenancy.exceptions import (
     TokenExpiredException,
     UserNotActiveException,
 )
-from models.database.user import User
+from app.modules.tenancy.models import User
 
 logger = logging.getLogger(__name__)
 

middleware/platform_context.py

@@ -22,7 +22,7 @@ from fastapi import Request
 from sqlalchemy.orm import Session
 
 from app.core.database import get_db
-from models.database.platform import Platform
+from app.modules.tenancy.models import Platform
 
 # Note: We use pure ASGI middleware (not BaseHTTPMiddleware) to enable path rewriting
 

middleware/theme_context.py

@@ -17,7 +17,7 @@ from sqlalchemy.orm import Session
 from starlette.middleware.base import BaseHTTPMiddleware
 
 from app.core.database import get_db
-from models.database.vendor_theme import VendorTheme
+from app.modules.cms.models import VendorTheme
 
 logger = logging.getLogger(__name__)
 

middleware/vendor_context.py

@@ -23,8 +23,8 @@ from starlette.middleware.base import BaseHTTPMiddleware
 
 from app.core.config import settings
 from app.core.database import get_db
-from models.database.vendor import Vendor
-from models.database.vendor_domain import VendorDomain
+from app.modules.tenancy.models import Vendor
+from app.modules.tenancy.models import VendorDomain
 
 logger = logging.getLogger(__name__)
 
@@ -319,7 +319,7 @@ class VendorContextManager:
             )
 
             if is_custom_domain:
-                from models.database.vendor_domain import VendorDomain
+                from app.modules.tenancy.models import VendorDomain
 
                 normalized_domain = VendorDomain.normalize_domain(referer_host)
                 logger.debug(