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

Emby.Server.Implementations/Data/CleanDatabaseScheduledTask.cs

@@ -108,14 +108,15 @@ public class CleanDatabaseScheduledTask : ILibraryPostScanTask
         var context = await _dbProvider.CreateDbContextAsync(cancellationToken).ConfigureAwait(false);
         await using (context.ConfigureAwait(false))
         {
-            var transaction = await context.Database.BeginTransactionAsync(cancellationToken).ConfigureAwait(false);
-            await using (transaction.ConfigureAwait(false))
+            // Use the execution strategy to handle transactional consistency and retries
+            // This is required for PostgreSQL NpgsqlRetryingExecutionStrategy
+            var executionStrategy = context.Database.CreateExecutionStrategy();
+            await executionStrategy.ExecuteAsync(async () =>
             {
                 await context.ItemValues.Where(e => e.BaseItemsMap!.Count == 0).ExecuteDeleteAsync(cancellationToken).ConfigureAwait(false);
                 subProgress.Report(50);
-                await transaction.CommitAsync(cancellationToken).ConfigureAwait(false);
                 subProgress.Report(100);
-            }
+            }).ConfigureAwait(false);
         }
 
         progress.Report(100);