fix(utils): Switch throttle decorator to async

After migration to async db operations, the throttle decorator also
needs to support async. Since the decorator is only used for async funcs
now, we can just switch it to async instead of supporting sync and async
at the same time.

Signed-off-by: Adam Tao <tcx4c70@gmail.com>

backend/open_webui/utils/misc.py

@@ -843,9 +843,9 @@ def throttle(interval: float = 10.0):
         last_calls = {}
         lock = threading.Lock()
 
-        def wrapper(*args, **kwargs):
+        async def wrapper(*args, **kwargs):
             if interval is None:
-                return func(*args, **kwargs)
+                return await func(*args, **kwargs)
 
             key = (args, freeze(kwargs))
             now = time.time()
@@ -855,7 +855,7 @@ def throttle(interval: float = 10.0):
                 if now - last_calls.get(key, 0) < interval:
                     return None
                 last_calls[key] = now
-            return func(*args, **kwargs)
+            return await func(*args, **kwargs)
 
         return wrapper