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/api/v1/admin/__init__.py

@@ -61,6 +61,7 @@ from . import (
     media,
     menu_config,
     messages,
+    module_config,
     modules,
     monitoring,
     notifications,
@@ -80,8 +81,9 @@ from . import (
 )
 
 # Import extracted module routers
-from app.modules.billing.routes import admin_router as billing_admin_router
-from app.modules.inventory.routes import admin_router as inventory_admin_router
+# NOTE: Import directly from admin.py files to avoid circular imports through __init__.py
+from app.modules.billing.routes.admin import admin_router as billing_admin_router
+from app.modules.inventory.routes.admin import admin_router as inventory_admin_router
 from app.modules.orders.routes.admin import admin_router as orders_admin_router
 from app.modules.orders.routes.admin import admin_exceptions_router as orders_exceptions_router
 from app.modules.marketplace.routes.admin import admin_router as marketplace_admin_router
@@ -129,6 +131,9 @@ router.include_router(menu_config.router, tags=["admin-menu-config"])
 # Include module management endpoints (super admin only)
 router.include_router(modules.router, tags=["admin-modules"])
 
+# Include module configuration endpoints (super admin only)
+router.include_router(module_config.router, tags=["admin-module-config"])
+
 
 # ============================================================================
 # User Management