Enhance download notifications and settings; add support for live activities

- Updated notification body to use proper German quotation marks for download failure alerts.
- Refactored audio interruption handling in PlayerEngine to utilize MainActor.assumeIsolated for better performance.
- Introduced nonisolated properties for support and downloads directories in ProgressSyncManager.
- Improved FullHistoryView and MainView with additional toolbar items and alerts for download failures.
- Added new toggles in SettingsView for parallel downloads and mobile data usage.
- Created new color assets for the DownloadWidgetExtension and updated widget appearance.
- Implemented Info.plist for DownloadWidgetExtension to support widget functionality.
- Enabled live activities support in iOS Info.plist.

ABS Client/Audiobookshelf swift/Services/NotificationManager.swift

@@ -29,7 +29,9 @@ final class NotificationManager {
 
         let content = UNMutableNotificationContent()
         content.title = "Download fehlgeschlagen"
-        content.body = "„\(itemTitle)" konnte nicht heruntergeladen werden."
+        // \u{201E} = „  (DOUBLE LOW-9 QUOTATION MARK, German opening)
+        // \u{201C} = "  (LEFT DOUBLE QUOTATION MARK, German closing)
+        content.body = "\u{201E}\(itemTitle)\u{201C} konnte nicht heruntergeladen werden."
         content.sound = .default
 
         let request = UNNotificationRequest(