Implement episode metadata management: add functionality to refresh episode metadata from external sources, including new API endpoints and UI integration. Enhance Show and Episode models to support additional metadata fields, and update database schema accordingly. Update ShowDetail and ShowMetadataCard components to display refreshed episode information and provide user feedback on metadata updates.

backend/src/TeleWave.Application/Common/Interfaces/IMetadataImageStore.cs

@@ -23,6 +23,15 @@ public interface IMetadataImageStore
 
     void DeleteShowImages(Guid showId);
 
+    /// <summary>Скачивает кадр серии по URL. Возвращает относительный путь или null при ошибке.</summary>
+    Task<string?> DownloadEpisodeStillAsync(
+        Guid episodeId,
+        string url,
+        CancellationToken cancellationToken
+    );
+
+    void DeleteEpisodeImages(Guid episodeId);
+
     /// <summary>Абсолютный путь к файлу по относительному (с защитой от traversal) или null, если вне корня.</summary>
     string? ResolveAbsolutePath(string relativePath);
 }