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/SettingsView.swift

@@ -10,6 +10,8 @@ struct SettingsView: View {
     @AppStorage("libraryLayout") private var layoutRaw: String = LibraryLayout.grid.rawValue
     @AppStorage("autoRefreshOnLaunch") private var autoRefreshOnLaunch: Bool = true
     @AppStorage("historyEnabled") private var historyEnabled: Bool = false
+    @AppStorage("downloadsParallel") private var downloadsParallel: Bool = true
+    @AppStorage("downloadsOverMobile") private var downloadsOverMobile: Bool = true
 
     @State private var showLogoutConfirm: Bool = false
     @State private var showHistoryDisableConfirm: Bool = false
@@ -226,10 +228,12 @@ struct SettingsView: View {
                 Text("\(app.downloads.downloadedItems.count) Einträge")
                     .foregroundStyle(.secondary)
             }
+            Toggle("Parallel herunterladen", isOn: $downloadsParallel)
+            Toggle("Download über Mobilnetz erlauben", isOn: $downloadsOverMobile)
         } header: {
             Text("Downloads")
         } footer: {
-            Text("Heruntergeladene Hörbücher und Folgen können einzeln über das Kontextmenü gelöscht werden.")
+            Text("Parallel lädt alle Tracks eines Hörbuchs gleichzeitig — schneller, aber höhere Server- und Netzlast. Bei deaktiviertem Mobilnetz starten Downloads erst wenn WLAN verfügbar ist.")
         }
     }
 
@@ -346,8 +350,13 @@ struct SettingsView: View {
 
     private var aboutPane: some View {
         Form {
-            LabeledContent("Version", value: appVersion)
-            LabeledContent("Heruntergeladen", value: "\(app.downloads.downloadedItems.count) Einträge")
+            Section("Downloads") {
+                Toggle("Parallel herunterladen", isOn: $downloadsParallel)
+                LabeledContent("Heruntergeladen", value: "\(app.downloads.downloadedItems.count) Einträge")
+            }
+            Section("Über") {
+                LabeledContent("Version", value: appVersion)
+            }
         }
         .formStyle(.grouped)
     }