feat: Implement file download token management and restructure file routes

- Added DownloadTokenManager for creating and verifying JWT download tokens.
- Introduced new download routes for creating download tokens and downloading files using tokens.
- Restructured file upload routes into a dedicated sub-router.
- Updated file upload session management with improved error handling and response structures.
- Created a new MCP (Microservice Communication Protocol) router with basic request and response models.
- Added base models for MCP requests and responses, including method enumeration.

middleware/auth.py

@@ -38,15 +38,6 @@ async def AuthRequired(
     except InvalidTokenError:
         raise credentials_exception
 
-async def SignRequired(
-    session: SessionDep,
-    token: Annotated[str, Depends(JWT.oauth2_scheme)],
-) -> User | None:
-    """
-    SignAuthRequired 需要验证请求签名
-    """
-    pass
-
 async def AdminRequired(
     user: Annotated[User, Depends(AuthRequired)],
 ) -> User: