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/messaging/models/__init__.py

@@ -2,7 +2,10 @@
 """
 Messaging module database models.
 
-This module contains the canonical implementations of messaging-related models.
+This module contains the canonical implementations of messaging-related models:
+- Message, Conversation: In-app messaging
+- AdminNotification: Admin notifications
+- Email templates and settings: Email system
 """
 
 from app.modules.messaging.models.message import (
@@ -14,13 +17,37 @@ from app.modules.messaging.models.message import (
     ParticipantType,
 )
 from app.modules.messaging.models.admin_notification import AdminNotification
+from app.modules.messaging.models.email import (
+    EmailCategory,
+    EmailLog,
+    EmailStatus,
+    EmailTemplate,
+)
+from app.modules.messaging.models.vendor_email_settings import (
+    EmailProvider,
+    PREMIUM_EMAIL_PROVIDERS,
+    VendorEmailSettings,
+)
+from app.modules.messaging.models.vendor_email_template import VendorEmailTemplate
 
 __all__ = [
+    # Conversations and messages
     "Conversation",
     "ConversationParticipant",
     "ConversationType",
     "Message",
     "MessageAttachment",
     "ParticipantType",
+    # Admin notifications
     "AdminNotification",
+    # Email templates
+    "EmailCategory",
+    "EmailLog",
+    "EmailStatus",
+    "EmailTemplate",
+    # Vendor email settings
+    "EmailProvider",
+    "PREMIUM_EMAIL_PROVIDERS",
+    "VendorEmailSettings",
+    "VendorEmailTemplate",
 ]