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>

models/database/__init__.py

@@ -1,5 +1,27 @@
 # models/database/__init__.py
-"""Database models package."""
+"""
+Database models package.
+
+This package imports all SQLAlchemy models to ensure they are registered
+with Base.metadata. This includes:
+1. Core models (defined in this directory)
+2. Module models (discovered from app/modules/<module>/models/)
+
+Module Model Discovery:
+- Modules can define their own models in app/modules/<module>/models/
+- These are automatically imported when this package loads
+- Module models must use `from app.core.database import Base`
+"""
+
+import importlib
+import logging
+from pathlib import Path
+
+logger = logging.getLogger(__name__)
+
+# ============================================================================
+# CORE MODELS (always loaded)
+# ============================================================================
 
 from .admin import (
     AdminAuditLog,
@@ -18,7 +40,6 @@ from .architecture_scan import (
 )
 from .base import Base
 from .company import Company
-from .content_page import ContentPage
 from .platform import Platform
 from .platform_module import PlatformModule
 from .vendor_platform import VendorPlatform
@@ -82,6 +103,49 @@ from .vendor import Role, Vendor, VendorUser
 from .vendor_domain import VendorDomain
 from .vendor_theme import VendorTheme
 
+# ============================================================================
+# MODULE MODELS (dynamically discovered)
+# ============================================================================
+
+
+def _discover_module_models():
+    """
+    Discover and import models from app/modules/<module>/models/ directories.
+
+    This ensures module models are registered with Base.metadata for:
+    1. Alembic migrations
+    2. SQLAlchemy queries
+
+    Module models must:
+    - Be in app/modules/<module>/models/__init__.py or individual files
+    - Import Base from app.core.database
+    """
+    modules_dir = Path(__file__).parent.parent.parent / "app" / "modules"
+
+    if not modules_dir.exists():
+        return
+
+    for module_dir in sorted(modules_dir.iterdir()):
+        if not module_dir.is_dir():
+            continue
+
+        models_init = module_dir / "models" / "__init__.py"
+        if models_init.exists():
+            module_name = f"app.modules.{module_dir.name}.models"
+            try:
+                importlib.import_module(module_name)
+                logger.debug(f"[Models] Loaded module models: {module_name}")
+            except ImportError as e:
+                logger.warning(f"[Models] Failed to import {module_name}: {e}")
+
+
+# Run discovery at import time
+_discover_module_models()
+
+# ============================================================================
+# EXPORTS
+# ============================================================================
+
 __all__ = [
     # Admin-specific models
     "AdminAuditLog",
@@ -113,8 +177,6 @@ __all__ = [
     "Role",
     "VendorDomain",
     "VendorTheme",
-    # Content
-    "ContentPage",
     # Platform
     "Platform",
     "PlatformModule",