Add retry extraction context menu, increase error text limit

- Right-click packages with extraction errors shows "Extraktion
  wiederholen" option to manually retry
- Increase WinRAR error text from 240 to 500 chars for better
  diagnostics in logs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/shared/preload-api.ts

@@ -42,6 +42,7 @@ export interface ElectronApi {
   exportBackup: () => Promise<{ saved: boolean }>;
   importBackup: () => Promise<{ restored: boolean; message: string }>;
   openLog: () => Promise<void>;
+  retryExtraction: (packageId: string) => Promise<void>;
   onStateUpdate: (callback: (snapshot: UiSnapshot) => void) => () => void;
   onClipboardDetected: (callback: (links: string[]) => void) => () => void;
   onUpdateInstallProgress: (callback: (progress: UpdateInstallProgress) => void) => () => void;