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/Configuration/config.js

@@ -16,6 +16,11 @@ const movieNightConfigPage = {
           config.EnablePeriodicSync !== false;
         view.querySelector("#EnablePlaybackEvents").checked =
           config.EnablePlaybackEvents !== false;
+
+        const uiScriptUrl = ApiClient.getUrl("web/ConfigurationPage", {
+          name: "MovieNight.ui.js",
+        });
+        view.querySelector("#UIScriptUrl").innerText = uiScriptUrl;
       })
       .finally(() => {
         Dashboard.hideLoadingMsg();