Refactor Jellyfin plugin: integrate UI components and implement backend contract.

- Integrated "Recommend Film" button and Rating UI into Jellyfin web interface via MutationObserver.
- Implemented full library sync (metadata + user state) in MovieNightSyncService.
- Updated MovieNightBackendClient to support sync, recommendations, ratings, and viewed status.
- Added proxy endpoints to MovieNightController for frontend-backend communication.
- Refined sync logic to handle large libraries and ensured .NET 9.0 compatibility.

Co-authored-by: devitq <118541411+devitq@users.noreply.github.com>

plugins/jellyfin/Jellyfin.Plugin.MovieNight/Plugin.cs

@@ -59,6 +59,14 @@ public class Plugin : BasePlugin<PluginConfiguration>, IHasWebPages
                     CultureInfo.InvariantCulture,
                     "{0}.Configuration.config.js",
                     GetType().Namespace)
+            },
+            new PluginPageInfo
+            {
+                Name = Name + ".ui.js",
+                EmbeddedResourcePath = string.Format(
+                    CultureInfo.InvariantCulture,
+                    "{0}.Configuration.ui.js",
+                    GetType().Namespace)
             }
         ];
     }