Encrypted backup system + hide extracted items in package list

Backup redesign (JDownloader 2 style):
- AES-256-GCM encrypted .mdd format with fixed app key
- All credentials exported (no more ***-masking), works on any PC
- Includes settings, session AND history in backup
- Backward-compatible: auto-detects legacy JSON backups
- Normalize history entries on import
- Added debridLinkApiKeys, linkSnappy credentials to sensitive keys

Hide extracted items:
- New setting: hide completed/extracted items from package item list
- Items still count in progress stats (done/total), only hidden in UI
- Default: enabled
- Toggle in settings: "Entpackte Items in Paketliste ausblenden"

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

src/main/storage.ts

@@ -371,6 +371,7 @@ export function normalizeSettings(settings: AppSettings): AppSettings {
       : defaults.accountListShowDetailedDebridLinkKeys,
     autoSortPackagesByProgress: settings.autoSortPackagesByProgress !== undefined ? Boolean(settings.autoSortPackagesByProgress) : defaults.autoSortPackagesByProgress,
     autoSkipExtracted: settings.autoSkipExtracted !== undefined ? Boolean(settings.autoSkipExtracted) : defaults.autoSkipExtracted,
+    hideExtractedItems: settings.hideExtractedItems !== undefined ? Boolean(settings.hideExtractedItems) : defaults.hideExtractedItems,
     confirmDeleteSelection: settings.confirmDeleteSelection !== undefined ? Boolean(settings.confirmDeleteSelection) : defaults.confirmDeleteSelection,
     totalDownloadedAllTime: typeof settings.totalDownloadedAllTime === "number" && settings.totalDownloadedAllTime >= 0 ? settings.totalDownloadedAllTime : defaults.totalDownloadedAllTime,
     theme: VALID_THEMES.has(settings.theme) ? settings.theme : defaults.theme,
@@ -906,7 +907,7 @@ export async function saveSessionAsync(paths: StoragePaths, session: SessionStat
 
 const MAX_HISTORY_ENTRIES = 500;
 
-function normalizeHistoryEntry(raw: unknown, index: number): HistoryEntry | null {
+export function normalizeHistoryEntry(raw: unknown, index: number): HistoryEntry | null {
   const entry = asRecord(raw);
   if (!entry) return null;