fix: invalidate playlist cache when schedule is updated

Playlist summary cache now refreshes immediately when sync schedules are changed.

allstarr/Controllers/AdminController.cs

@@ -1528,6 +1528,12 @@ public class AdminController : ControllerBase
             
             _logger.LogInformation("Config file updated successfully at {Path}", _envFilePath);
             
+            // Invalidate playlist summary cache if playlists were updated
+            if (appliedUpdates.Contains("SPOTIFY_IMPORT_PLAYLISTS"))
+            {
+                InvalidatePlaylistSummaryCache();
+            }
+            
             return Ok(new
             {
                 message = "Configuration updated. Restart container to apply changes.",