Add voice analytics filters and metrics

backend/app/api/admin_providers.py

@@ -1,3 +1,5 @@
+from typing import Literal
+
 from fastapi import APIRouter, Depends, HTTPException, Query
 from pydantic import BaseModel, ConfigDict, Field
 from sqlalchemy import select
@@ -120,7 +122,9 @@ async def list_provider_capabilities():
 @router.get("/providers/analytics", response_model=ProviderAnalyticsResponse)
 async def get_provider_analytics(
     days: int | None = Query(default=None, ge=1, le=365),
-    capability: str | None = Query(default=None),
+    capability: Literal["text", "image", "tts", "storybook", "asr"] | None = Query(
+        default=None
+    ),
     db: AsyncSession = Depends(get_db),
 ):
     """获取当前环境跨用户的 Provider 运营摘要。"""