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.

Jellyfin.Server.Implementations/Item/MediaStreamRepository.cs

@@ -9,6 +9,7 @@ using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using Jellyfin.Database.Implementations;
 using Jellyfin.Database.Implementations.Entities;
 using MediaBrowser.Controller;
@@ -40,23 +41,33 @@ public class MediaStreamRepository : IMediaStreamRepository
     }
 
     /// <inheritdoc />
-    public void SaveMediaStreams(Guid id, IReadOnlyList<MediaStream> streams, CancellationToken cancellationToken)
+    public async Task SaveMediaStreamsAsync(Guid id, IReadOnlyList<MediaStream> streams, CancellationToken cancellationToken = default)
     {
-        using var context = _dbProvider.CreateDbContext();
-        using var transaction = context.Database.BeginTransaction();
+        await using var context = _dbProvider.CreateDbContext();
+        await using var transaction = await context.Database.BeginTransactionAsync(cancellationToken).ConfigureAwait(false);
 
-        context.MediaStreamInfos.Where(e => e.ItemId.Equals(id)).ExecuteDelete();
-        context.MediaStreamInfos.AddRange(streams.Select(f => Map(f, id)));
-        context.SaveChanges();
+        await context.MediaStreamInfos
+            .Where(e => e.ItemId.Equals(id))
+            .ExecuteDeleteAsync(cancellationToken)
+            .ConfigureAwait(false);
 
-        transaction.Commit();
+        await context.MediaStreamInfos
+            .AddRangeAsync(streams.Select(f => Map(f, id)), cancellationToken)
+            .ConfigureAwait(false);
+
+        await context.SaveChangesAsync(cancellationToken).ConfigureAwait(false);
+        await transaction.CommitAsync(cancellationToken).ConfigureAwait(false);
     }
 
     /// <inheritdoc />
-    public IReadOnlyList<MediaStream> GetMediaStreams(MediaStreamQuery filter)
+    public async Task<IReadOnlyList<MediaStream>> GetMediaStreamsAsync(MediaStreamQuery filter, CancellationToken cancellationToken = default)
     {
-        using var context = _dbProvider.CreateDbContext();
-        return TranslateQuery(context.MediaStreamInfos.AsNoTracking(), filter).AsEnumerable().Select(Map).ToArray();
+        await using var context = _dbProvider.CreateDbContext();
+        var streams = await TranslateQuery(context.MediaStreamInfos.AsNoTracking(), filter)
+            .ToArrayAsync(cancellationToken)
+            .ConfigureAwait(false);
+
+        return streams.Select(Map).ToArray();
     }
 
     private string? GetPathToSave(string? path)