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/core/static/admin/js/dashboard.js

@@ -25,6 +25,9 @@ function adminDashboard() {
          * Initialize dashboard
          */
         async init() {
+            // Load i18n translations
+            await I18n.loadModule('core');
+
             // Guard against multiple initialization
             if (window._dashboardInitialized) {
                 dashLog.warn('Dashboard already initialized, skipping...');
@@ -79,7 +82,7 @@ function adminDashboard() {
             } catch (error) {
                 window.LogConfig.logError(error, 'Dashboard Load');
                 this.error = error.message;
-                Utils.showToast('Failed to load dashboard data', 'error');
+                Utils.showToast(I18n.t('core.messages.failed_to_load_dashboard_data'), 'error');
 
             } finally {
                 this.loading = false;
@@ -182,7 +185,7 @@ function adminDashboard() {
         async refresh() {
             dashLog.info('=== DASHBOARD REFRESH TRIGGERED ===');
             await this.loadDashboard();
-            Utils.showToast('Dashboard refreshed', 'success');
+            Utils.showToast(I18n.t('core.messages.dashboard_refreshed'), 'success');
             dashLog.info('=== DASHBOARD REFRESH COMPLETE ===');
         }
     };