Backend: - Add provider/model/key types and routes to ai.api + base.api - Generate 11 handler + logic stubs via goctl - Implement provider CRUD logic (list/create/update/delete) - Implement model admin CRUD logic (create/update/delete) - Implement API key CRUD logic (list/create/update/delete) - Add Casbin policies for key management and admin endpoints - Add menu seeds with proper icons (Cpu, Key, MessageSquare) Frontend: - Add provider/model/key TypeScript types and API client methods - Create AIModelManagementPage with provider + model tabs - Create AIKeyManagementPage with key CRUD and provider dropdown - Register routes and page titles for /ai/models and /ai/keys - Add Cpu, Key, MessageSquare icons to Sidebar icon map