feat(api): add unified Models API endpoint

- Add models_service.py with model query logic and caching
- Add models.py unified endpoint supporting Claude/OpenAI/Gemini formats
- Auto-detect API format based on request headers
- Support /v1/models and /v1beta/models (Gemini) paths
- Update route registration and comments

src/api/public/__init__.py

@@ -6,10 +6,13 @@ from .capabilities import router as capabilities_router
 from .catalog import router as catalog_router
 from .claude import router as claude_router
 from .gemini import router as gemini_router
+from .models import router as models_router
 from .openai import router as openai_router
 from .system_catalog import router as system_catalog_router
 
 router = APIRouter()
+# Models API 需要在最前面注册，避免被其他路由的 path 参数捕获
+router.include_router(models_router)
 router.include_router(claude_router, tags=["Claude API"])
 router.include_router(openai_router)
 router.include_router(gemini_router, tags=["Gemini API"])