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/Views/MainView.swift

@@ -116,6 +116,21 @@ struct MainView: View {
                 FullHistoryView()
                     .environment(app)
             }
+            #if os(iOS)
+            .alert(
+                "Download fehlgeschlagen",
+                isPresented: Binding(
+                    get: { app.downloads.downloadFailureAlertTitle != nil },
+                    set: { if !$0 { app.downloads.downloadFailureAlertTitle = nil } }
+                )
+            ) {
+                Button("OK") { app.downloads.downloadFailureAlertTitle = nil }
+            } message: {
+                if let title = app.downloads.downloadFailureAlertTitle {
+                    Text("\u{201E}\(title)\u{201C} konnte nicht heruntergeladen werden.")
+                }
+            }
+            #endif
     }
 
     @ViewBuilder