Refactor PostgreSQL provider: multi-schema & async prep

- Refactor migrations and provider to use multiple PostgreSQL schemas, each matching a legacy SQLite database (activitylog, authentication, displaypreferences, library, users).
- All tables, foreign keys, and indexes are now schema-qualified; Down migration drops tables by schema.
- Provider ensures schemas exist before migrations; entities are mapped to correct schemas in OnModelCreating.
- Add support for max-pool-size, min-pool-size, and multiplexing connection options; update logging accordingly.
- VACUUM ANALYZE now runs per schema during scheduled optimization.
- TruncateAllTablesAsync now truncates tables with schema qualification.
- README updated with schema structure, new options, and multiplexing warnings.
- CacheDecorator now calls async repository methods using .GetAwaiter().GetResult(), with documentation.
- Lays groundwork for full async/await and multiplexing support in the database layer.

MediaBrowser.Controller/Persistence/IKeyframeRepository.cs

@@ -16,11 +16,12 @@ using Jellyfin.MediaEncoding.Keyframes;
 public interface IKeyframeRepository
 {
     /// <summary>
-    /// Gets the keyframe data.
+    /// Gets the keyframe data asynchronously.
     /// </summary>
     /// <param name="itemId">The item id.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
     /// <returns>The keyframe data.</returns>
-    IReadOnlyList<KeyframeData> GetKeyframeData(Guid itemId);
+    Task<IReadOnlyList<KeyframeData>> GetKeyframeDataAsync(Guid itemId, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Saves the keyframe data.