feat(ios): add iOS 26+ continued processing and Live Activities (#1514)

ui/flutter/lib/api/model/downloader_config.dart

@@ -125,6 +125,7 @@ class ExtraConfig {
   bool notifyWhenNewVersion;
   bool desktopNotification;
   bool backgroundLocationKeepAlive;
+  bool backgroundContinuedProcessing;
   WindowStateConfig windowState;
   Map<String, String> bookmarks;
   List<String> createHistory;
@@ -146,6 +147,7 @@ class ExtraConfig {
     this.notifyWhenNewVersion = true,
     this.desktopNotification = true,
     this.backgroundLocationKeepAlive = false,
+    this.backgroundContinuedProcessing = false,
     WindowStateConfig? windowState,
     this.bookmarks = const {},
     this.createHistory = const [],

ui/flutter/lib/api/model/downloader_config.g.dart

@@ -119,6 +119,10 @@ ExtraConfig _$ExtraConfigFromJson(Map<String, dynamic> json) =>
         notifyWhenNewVersion: json['notifyWhenNewVersion'] as bool? ?? true,
         desktopNotification: json['desktopNotification'] as bool? ?? true,
         backgroundLocationKeepAlive: json['backgroundLocationKeepAlive'] as bool? ?? false,
+        backgroundContinuedProcessing:
+            json['backgroundContinuedProcessing']
+                as bool? ??
+            false,
         windowState: json['windowState'] == null
             ? null
             : WindowStateConfig.fromJson(json['windowState'] as Map<String, dynamic>?),
@@ -146,6 +150,8 @@ Map<String, dynamic> _$ExtraConfigToJson(ExtraConfig instance) => <String, dynam
   'notifyWhenNewVersion': instance.notifyWhenNewVersion,
   'desktopNotification': instance.desktopNotification,
   'backgroundLocationKeepAlive': instance.backgroundLocationKeepAlive,
+  'backgroundContinuedProcessing':
+      instance.backgroundContinuedProcessing,
   'windowState': instance.windowState.toJson(),
   'bookmarks': instance.bookmarks,
   'createHistory': instance.createHistory,