feat: improve auth error logging with exception type details

backend/auth.py

@@ -68,8 +68,8 @@ def _decode_token(token: str, jwks):
     except HTTPException:
         raise
     except Exception as exc:
-        logger.warning("Token verification failed", error=str(exc))
-        raise HTTPException(status_code=401, detail="Invalid token") from None
+        logger.warning("Token verification failed", error_type=type(exc).__name__, error=str(exc))
+        raise HTTPException(status_code=401, detail=f"Invalid token ({type(exc).__name__})") from None
 
 
 def require_auth(authorization: str | None = Header(None)):