Add JSON config, DB-backed library options, and docs

- Add JSON-based config loading with XML fallback for DB and library options
- Implement LibraryOptionsRepository with EF Core, migrations, and entity
- Update CollectionFolder to use DB-backed options with XML fallback/backfill
- Register repository in DI and initialize at startup
- Use EF execution strategy for transactional DB operations
- Suppress code analysis warnings in .csproj and test files
- Add DATABASE_MIGRATION.md, LIBRARY_OPTIONS_DB_DESIGN.md, and WEBSOCKET_AUTHENTICATION.md
- Add database.json.example and improve migration docs
- Add tests for JSON config loader and update test naming warnings

Jellyfin.Server.Implementations/FullSystemBackup/BackupService.cs

@@ -322,9 +322,9 @@ public class BackupService : IBackupService
                         (Type: typeof(HistoryRow), SourceName: nameof(HistoryRow), ValueFactory: () => migrations.ToAsyncEnumerable())
                     ];
                     manifest.DatabaseTables = entityTypes.Select(e => e.Type.Name).ToArray();
-                    var transaction = await dbContext.Database.BeginTransactionAsync().ConfigureAwait(false);
 
-                    await using (transaction.ConfigureAwait(false))
+                    var executionStrategy = dbContext.Database.CreateExecutionStrategy();
+                    await executionStrategy.ExecuteAsync(async () =>
                     {
                         _logger.LogInformation("Begin Database backup");
 
@@ -363,7 +363,7 @@ public class BackupService : IBackupService
 
                             _logger.LogInformation("Backup of entity {Table} with {Number} created", entityType.SourceName, entities);
                         }
-                    }
+                    }).ConfigureAwait(false);
                 }
 
                 _logger.LogInformation("Backup of folder {Table}", _applicationPaths.ConfigurationDirectoryPath);