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/cms/static/admin/js/content-pages.js

@@ -28,6 +28,9 @@ function contentPagesManager() {
 
         // Initialize
         async init() {
+            // Load i18n translations
+            await I18n.loadModule('cms');
+
             contentPagesLog.info('=== CONTENT PAGES MANAGER INITIALIZING ===');
 
             // Prevent multiple initializations
@@ -235,7 +238,7 @@ function contentPagesManager() {
 
             } catch (err) {
                 contentPagesLog.error('Error deleting page:', err);
-                Utils.showToast(`Failed to delete page: ${err.message}`, 'error');
+                Utils.showToast(I18n.t('cms.messages.failed_to_delete_page', { error: err.message }), 'error');
             }
         },