Implement user onboarding and enhanced .strm file creation

- Added automated onboarding dialog for new users to pick genres, eras, and content types.
- Enhanced "Add Movie" functionality to support folder-per-movie structure with Year and IMDb ID.
- Improved ui.js with custom dialogs for Onboarding, Rating, and Adding Movies.
- Fixed API accessibility by using standard [Authorize] attributes.
- Added "Mark Viewed" and "Sync" actions to the UI.

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

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

@@ -167,6 +167,34 @@ public class MovieNightBackendClient
         return body;
     }
 
+    /// <summary>
+    /// Gets user preferences.
+    /// </summary>
+    public async Task<string?> GetPreferencesAsync(string userId, CancellationToken cancellationToken)
+    {
+        var request = CreateRequest(HttpMethod.Get, $"/api/users/{userId}/preferences");
+        if (request is null) return null;
+
+        using var response = await _httpClient.SendAsync(request, cancellationToken).ConfigureAwait(false);
+        if (response.StatusCode == System.Net.HttpStatusCode.NotFound) return null;
+
+        var body = await response.Content.ReadAsStringAsync(cancellationToken).ConfigureAwait(false);
+        return body;
+    }
+
+    /// <summary>
+    /// Completes onboarding for a user.
+    /// </summary>
+    public async Task CompleteOnboardingAsync(string userId, object payload, CancellationToken cancellationToken)
+    {
+        var request = CreateRequest(HttpMethod.Post, $"/api/users/{userId}/recommendation-onboarding");
+        if (request is null) return;
+
+        request.Content = JsonContent.Create(payload, options: JsonOptions);
+        using var response = await _httpClient.SendAsync(request, cancellationToken).ConfigureAwait(false);
+        response.EnsureSuccessStatusCode();
+    }
+
     /// <summary>
     /// Pushes an event payload to the backend event endpoint.
     /// </summary>