feat: complete modular platform architecture (Phases 1-5)

Phase 1 - Vendor Router Integration:
- Wire up vendor module routers in app/api/v1/vendor/__init__.py
- Use lazy imports via __getattr__ to avoid circular dependencies

Phase 2 - Extract Remaining Modules:
- Create 6 new module directories: customers, cms, analytics, messaging,
  dev_tools, monitoring
- Each module has definition.py and route wrappers
- Update registry to import from extracted modules

Phase 3 - Database Table Migration:
- Add PlatformModule junction table for auditable module tracking
- Add migration zc2m3n4o5p6q7_add_platform_modules_table.py
- Add modules relationship to Platform model
- Update ModuleService with JSON-to-junction-table migration

Phase 4 - Module-Specific Configuration UI:
- Add /api/v1/admin/module-config/* endpoints
- Add module-config.html template and JS

Phase 5 - Integration Tests:
- Add tests/fixtures/module_fixtures.py
- Add tests/integration/api/v1/admin/test_modules.py
- Add tests/integration/api/v1/modules/test_module_access.py

Architecture fixes:
- Fix JS-003 errors: use ...data() directly in Alpine components
- Fix JS-005 warnings: add init() guards to prevent duplicate init
- Fix API-001 errors: add MenuActionResponse Pydantic model
- Add FE-008 noqa for dynamic number input in template

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

app/modules/cms/routes/admin.py

@@ -0,0 +1,25 @@
+# app/modules/cms/routes/admin.py
+"""
+CMS module admin routes.
+
+This module wraps the existing admin content pages routes and adds
+module-based access control. Routes are re-exported from the
+original location with the module access dependency.
+"""
+
+from fastapi import APIRouter, Depends
+
+from app.api.deps import require_module_access
+
+# Import original router (direct import to avoid circular dependency)
+from app.api.v1.admin.content_pages import router as original_router
+
+# Create module-aware router
+admin_router = APIRouter(
+    prefix="/content-pages",
+    dependencies=[Depends(require_module_access("cms"))],
+)
+
+# Re-export all routes from the original module with module access control
+for route in original_router.routes:
+    admin_router.routes.append(route)