remove old import

app/services/cache.py

@@ -12,10 +12,11 @@ from typing import Any, Optional
 
 try:
     import redis.asyncio as redis  # type: ignore
-except Exception:  # pragma: no cover - allow running without redis installed
+except ImportError:  # pragma: no cover - allow running without redis installed
     redis = None  # type: ignore
 
 from app.config import settings
+from app.utils.logging import app_logger
 
 
 _client: Optional["redis.Redis"] = None  # type: ignore
@@ -35,14 +36,15 @@ async def _get_client() -> Optional["redis.Redis"]:  # type: ignore
         if _client is None:
             try:
                 _client = redis.from_url(settings.redis_url, decode_responses=True)  # type: ignore
-            except Exception:
+            except Exception as e:
+                app_logger.debug(f"Redis connection failed: {str(e)}")
                 _client = None
     return _client
 
 
 def _stable_hash(obj: Any) -> str:
     data = json.dumps(obj, sort_keys=True, separators=(",", ":"))
-    return hashlib.sha1(data.encode("utf-8")).hexdigest()
+    return hashlib.sha256(data.encode("utf-8")).hexdigest()
 
 
 def build_key(kind: str, user_id: Optional[str], parts: dict) -> str: