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>

static/admin/js/platform-modules.js

@@ -4,12 +4,9 @@
 const moduleConfigLog = window.LogConfig?.loggers?.moduleConfig || window.LogConfig?.createLogger?.('moduleConfig') || console;
 
 function adminPlatformModules(platformCode) {
-    // Get base data with safety check for standalone usage
-    const baseData = typeof data === 'function' ? data() : {};
-
     return {
         // Inherit base layout functionality from init-alpine.js
-        ...baseData,
+        ...data(),
 
         // Page-specific state
         currentPage: 'platforms',
@@ -62,6 +59,13 @@ function adminPlatformModules(platformCode) {
         },
 
         async init() {
+            // Guard against duplicate initialization
+            if (window._platformModulesInitialized) {
+                moduleConfigLog.warn('Already initialized, skipping');
+                return;
+            }
+            window._platformModulesInitialized = true;
+
             moduleConfigLog.info('=== PLATFORM MODULES PAGE INITIALIZING ===');
             moduleConfigLog.info('Platform code:', this.platformCode);