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/schemas/image.py

@@ -0,0 +1,46 @@
+# app/modules/cms/schemas/image.py
+"""
+Pydantic schemas for image operations.
+"""
+
+from pydantic import BaseModel
+
+
+class ImageUrls(BaseModel):
+    """URLs for image variants."""
+
+    original: str
+    medium: str | None = None  # 800px variant
+    thumb: str | None = None  # 200px variant
+
+    # Allow arbitrary keys for flexibility
+    class Config:
+        extra = "allow"
+
+
+class ImageUploadResponse(BaseModel):
+    """Response from image upload."""
+
+    success: bool
+    image: dict | None = None
+    error: str | None = None
+
+
+class ImageDeleteResponse(BaseModel):
+    """Response from image deletion."""
+
+    success: bool
+    message: str
+
+
+class ImageStorageStats(BaseModel):
+    """Image storage statistics."""
+
+    total_files: int
+    total_size_bytes: int
+    total_size_mb: float
+    total_size_gb: float
+    directory_count: int
+    max_files_per_dir: int
+    avg_files_per_dir: float
+    products_estimated: int