fix: user group pagination reset and model image caching (#19959)

- Changed default sort order in 'Edit Group' modal to 'created_at' (newest first).
  Previously it sorted by group membership, causing toggled users to invisible jump
  to the top of the list (often changing pages). using a stable sort fixes this UX issue.
- Removed unnecessary `page = 1` reset in toggleMember function so admins
  don't lose their place when selecting multiple users.

Bug 2 - Model Image Display Bug:
- Added `Cache-Control: no-cache, must-revalidate` headers to the model profile
  image endpoint. This ensures that when a model avatar is updated, the browser
  fetches the new image instead of serving a stale cached version (favicon).

Fixes #19885

backend/open_webui/routers/models.py

@@ -291,12 +291,15 @@ async def get_model_by_id(id: str, user=Depends(get_verified_user)):
 @router.get("/model/profile/image")
 async def get_model_profile_image(id: str, user=Depends(get_verified_user)):
     model = Models.get_model_by_id(id)
+    # Cache-control headers to prevent stale cached images
+    cache_headers = {"Cache-Control": "no-cache, must-revalidate"}
+
     if model:
         if model.meta.profile_image_url:
             if model.meta.profile_image_url.startswith("http"):
                 return Response(
                     status_code=status.HTTP_302_FOUND,
-                    headers={"Location": model.meta.profile_image_url},
+                    headers={"Location": model.meta.profile_image_url, **cache_headers},
                 )
             elif model.meta.profile_image_url.startswith("data:image"):
                 try:
@@ -307,14 +310,17 @@ async def get_model_profile_image(id: str, user=Depends(get_verified_user)):
                     return StreamingResponse(
                         image_buffer,
                         media_type="image/png",
-                        headers={"Content-Disposition": "inline; filename=image.png"},
+                        headers={
+                            "Content-Disposition": "inline; filename=image.png",
+                            **cache_headers,
+                        },
                     )
                 except Exception as e:
                     pass
 
-        return FileResponse(f"{STATIC_DIR}/favicon.png")
+        return FileResponse(f"{STATIC_DIR}/favicon.png", headers=cache_headers)
     else:
-        return FileResponse(f"{STATIC_DIR}/favicon.png")
+        return FileResponse(f"{STATIC_DIR}/favicon.png", headers=cache_headers)
 
 
 ############################

src/lib/components/admin/Users/Groups/Users.svelte

@@ -30,7 +30,7 @@
 	let total = null;
 
 	let query = '';
-	let orderBy = `group_id:${groupId}`; // default sort key
+	let orderBy = 'created_at'; // default sort key
 	let direction = 'desc'; // default sort order
 
 	let page = 1;
@@ -42,6 +42,7 @@
 			orderBy = key;
 			direction = 'asc';
 		}
+		page = 1;
 	};
 
 	const getUserList = async () => {
@@ -75,7 +76,6 @@
 			});
 		}
 
-		page = 1;
 		getUserList();
 	};