feat: Recently Added Guard plugin for Jellyfin 12.2

Keeps Radarr/Sonarr quality upgrades out of "Recently Added" by keeping
a ledger of the first date added per logical medium (movie or episode,
identified by provider ids and the series) and restoring it on upgrades.

- core logic without Jellyfin types (Reconciler, MediaKeys, GuardProcessor)
- thread-safe ledger with atomic, debounced persistence
- event processing via channel and background worker, seed on first start
- scheduled task "Ledger synchronisieren", status API, configuration page
- xUnit tests and a Jellyfin 12.2 integration test
- Gitea workflows: build/test, release with jprm and manifest branch

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Jellyfin.Plugin.RecentlyAddedGuard/PluginServiceRegistrator.cs

@@ -0,0 +1,50 @@
+using System;
+using System.IO;
+using Jellyfin.Plugin.RecentlyAddedGuard.Core;
+using Jellyfin.Plugin.RecentlyAddedGuard.Ledger;
+using Jellyfin.Plugin.RecentlyAddedGuard.Services;
+using MediaBrowser.Common.Configuration;
+using MediaBrowser.Controller;
+using MediaBrowser.Controller.Plugins;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+
+namespace Jellyfin.Plugin.RecentlyAddedGuard;
+
+/// <summary>
+/// Registers the plugin services with Jellyfin's DI container.
+/// </summary>
+public class PluginServiceRegistrator : IPluginServiceRegistrator
+{
+    /// <inheritdoc />
+    public void RegisterServices(IServiceCollection serviceCollection, IServerApplicationHost applicationHost)
+    {
+        // Runs before the plugin instance exists; factories are evaluated later, when the host starts.
+        serviceCollection.AddSingleton<CorrectionLog>();
+        serviceCollection.AddSingleton(sp => new LedgerStore(
+            Path.Combine(GetDataFolderPath(sp), LedgerStore.DefaultFileName),
+            sp.GetRequiredService<ILogger<LedgerStore>>()));
+        serviceCollection.AddSingleton(sp => new Reconciler(
+            sp.GetRequiredService<LedgerStore>(),
+            GetOptions,
+            TimeProvider.System,
+            sp.GetRequiredService<ILogger<Reconciler>>()));
+        serviceCollection.AddSingleton<IdentityResolver>();
+        serviceCollection.AddSingleton<LibraryItemDateWriter>();
+        serviceCollection.AddSingleton(sp => new GuardProcessor(
+            sp.GetRequiredService<Reconciler>(),
+            sp.GetRequiredService<LibraryItemDateWriter>(),
+            sp.GetRequiredService<CorrectionLog>(),
+            GetOptions,
+            TimeProvider.System,
+            sp.GetRequiredService<ILogger<GuardProcessor>>()));
+        serviceCollection.AddSingleton<LedgerSynchronizer>();
+        serviceCollection.AddHostedService<GuardHostedService>();
+    }
+
+    private static GuardOptions GetOptions() => Plugin.CurrentConfiguration.ToGuardOptions();
+
+    private static string GetDataFolderPath(IServiceProvider serviceProvider)
+        => Plugin.Instance?.DataFolderPath
+            ?? Path.Combine(serviceProvider.GetRequiredService<IApplicationPaths>().PluginsPath, typeof(Plugin).Assembly.GetName().Name!);
+}