refactor: separate provider capability policy

backend/app/api/admin_providers.py

@@ -8,7 +8,7 @@ from app.db.admin_models import Provider
 from app.db.database import get_db
 from app.services.adapters.registry import AdapterRegistry
 from app.services.cost_tracker import cost_tracker
-from app.services.provider_router import DEFAULT_PROVIDERS
+from app.services.provider_policy import DEFAULT_PROVIDERS, list_capability_policies
 from app.services.secret_service import SecretService
 
 router = APIRouter(dependencies=[Depends(admin_guard)])
@@ -68,6 +68,12 @@ async def get_env_defaults():
     return DEFAULT_PROVIDERS
 
 
+@router.get("/providers/capabilities")
+async def list_provider_capabilities():
+    """获取 Provider 能力分层与默认路由策略。"""
+    return list_capability_policies()
+
+
 @router.get("/providers", response_model=list[ProviderResponse])
 async def list_providers(db: AsyncSession = Depends(get_db)):
     result = await db.execute(select(Provider))