feat(antigravity): 自动设置隐私并支持后台手动重试

新增 Antigravity OAuth 隐私设置能力，在账号创建、刷新、导入和后台
Token 刷新路径自动调用 setUserSettings + fetchUserInfo 关闭遥测；
持久化后同步内存 Extra，错误处理改为日志记录。

Made-with: Cursor

frontend/src/i18n/locales/en.ts

@@ -1984,6 +1984,9 @@ export default {
       privacyTrainingOff: 'Training data sharing disabled',
       privacyCfBlocked: 'Blocked by Cloudflare, training may still be on',
       privacyFailed: 'Failed to disable training',
+      privacyAntigravitySet: 'Telemetry and marketing emails disabled',
+      privacyAntigravityFailed: 'Privacy setting failed',
+      setPrivacy: 'Set Privacy',
       // Capacity status tooltips
       capacity: {
         windowCost: {