feat: complete CMS as fully autonomous self-contained module

Transform CMS from a thin wrapper into a fully self-contained module with
all code living within app/modules/cms/:

Module Structure:
- models/: ContentPage model (canonical location with dynamic discovery)
- schemas/: Pydantic schemas for API validation
- services/: ContentPageService business logic
- exceptions/: Module-specific exceptions
- routes/api/: REST API endpoints (admin, vendor, shop)
- routes/pages/: HTML page routes (admin, vendor)
- templates/cms/: Jinja2 templates (namespaced)
- static/: JavaScript files (admin/vendor)
- locales/: i18n translations (en, fr, de, lb)

Key Changes:
- Move ContentPage model to module with dynamic model discovery
- Create Pydantic schemas package for request/response validation
- Extract API routes from app/api/v1/*/ to module
- Extract page routes from admin_pages.py/vendor_pages.py to module
- Move static JS files to module with dedicated mount point
- Update templates to use cms_static for module assets
- Add module static file mounting in main.py
- Delete old scattered files (no shims - hard errors on old imports)

This establishes the pattern for migrating other modules to be
fully autonomous and independently deployable.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/create_default_content_pages.py

@@ -37,7 +37,7 @@ from sqlalchemy import select
 from sqlalchemy.orm import Session
 
 from app.core.database import SessionLocal
-from models.database.content_page import ContentPage
+from app.modules.cms.models import ContentPage
 
 # ============================================================================
 # DEFAULT PAGE CONTENT

scripts/create_landing_page.py

@@ -17,7 +17,7 @@ from datetime import UTC, datetime
 from sqlalchemy.orm import Session
 
 from app.core.database import SessionLocal
-from models.database.content_page import ContentPage
+from app.modules.cms.models import ContentPage
 from models.database.vendor import Vendor
 
 

scripts/create_platform_pages.py

@@ -24,7 +24,7 @@ project_root = Path(__file__).resolve().parent.parent
 sys.path.insert(0, str(project_root))
 
 from app.core.database import SessionLocal
-from app.services.content_page_service import content_page_service
+from app.modules.cms.services import content_page_service
 
 
 def create_platform_pages():
@@ -38,7 +38,7 @@ def create_platform_pages():
         print()
 
         # Import ContentPage for checking existing pages
-        from models.database.content_page import ContentPage
+        from app.modules.cms.models import ContentPage
 
         # ========================================================================
         # 1. PLATFORM HOMEPAGE

scripts/seed_demo.py

@@ -51,9 +51,9 @@ from app.core.config import settings
 from app.core.database import SessionLocal
 from app.core.environment import get_environment, is_production
 from middleware.auth import AuthManager
+from app.modules.cms.models import ContentPage
 from models.database.admin import PlatformAlert
 from models.database.company import Company
-from models.database.content_page import ContentPage
 from models.database.customer import Customer, CustomerAddress
 from models.database.marketplace_import_job import MarketplaceImportJob
 from models.database.marketplace_product import MarketplaceProduct