fix(redis): Validate REDIS_URL format in Redis client settings

app/cache.py

@@ -28,9 +28,12 @@ def create_redis_connection(**kwargs) -> redis.Redis:
 # -----------------------------------------------------------------------------
 def _redis_from_settings() -> redis.Redis:
     """Create Redis client from settings using insightfy patterns."""
-    if CACHE_URL:
+    cache_url = (CACHE_URL or "").strip()
+    if cache_url:
+        if not cache_url.startswith(("redis://", "rediss://", "unix://")):
+            raise ValueError("REDIS_URL must start with redis://, rediss://, or unix://")
         return redis.from_url(
-            CACHE_URL,
+            cache_url,
             decode_responses=True,
             socket_timeout=5,
             socket_connect_timeout=5,