Fix Jellyfin BadRequest errors when fetching playlist items

- Add UserId parameter to playlist items API call (required by Jellyfin)
- Auto-fetch first user if no user ID configured
- Simplify Fields parameter to only request Path
- This fixes the 400 BadRequest errors when loading Jellyfin playlists tab

allstarr/Controllers/AdminController.cs

@@ -826,7 +826,36 @@ public class AdminController : ControllerBase
     {
         try
         {
-            var url = $"{_jellyfinSettings.Url}/Playlists/{playlistId}/Items?Fields=ProviderIds,Path,MediaSources";
+            // Jellyfin requires a UserId to fetch playlist items
+            // We'll use the first available user if not specified
+            var userId = _jellyfinSettings.UserId;
+            
+            // If no user configured, try to get the first user
+            if (string.IsNullOrEmpty(userId))
+            {
+                var usersResponse = await _jellyfinHttpClient.SendAsync(new HttpRequestMessage(HttpMethod.Get, $"{_jellyfinSettings.Url}/Users")
+                {
+                    Headers = { { "X-Emby-Authorization", GetJellyfinAuthHeader() } }
+                });
+                
+                if (usersResponse.IsSuccessStatusCode)
+                {
+                    var usersJson = await usersResponse.Content.ReadAsStringAsync();
+                    using var usersDoc = JsonDocument.Parse(usersJson);
+                    if (usersDoc.RootElement.GetArrayLength() > 0)
+                    {
+                        userId = usersDoc.RootElement[0].GetProperty("Id").GetString();
+                    }
+                }
+            }
+            
+            if (string.IsNullOrEmpty(userId))
+            {
+                _logger.LogWarning("No user ID available to fetch playlist items for {PlaylistId}", playlistId);
+                return (0, 0, 0);
+            }
+            
+            var url = $"{_jellyfinSettings.Url}/Playlists/{playlistId}/Items?UserId={userId}&Fields=Path";
             var request = new HttpRequestMessage(HttpMethod.Get, url);
             request.Headers.Add("X-Emby-Authorization", GetJellyfinAuthHeader());