feat(privacy): add personalized ads toggle in settings

- Add PrivacySettings schema with can_sell field (default: false)
- Move privacy toggle to GeneralSettingsScreen with clear labeling
- Update l10n for zh/en/zh_hant with user-friendly copy
- Clean up redundant PrivacyNotificationSettingsScreen
- Update profile-protocol.md to reflect new privacy schema
- Fix basedpyright warnings in user.py

apps/lib/l10n/app_en.arb

@@ -483,5 +483,9 @@
   "settingsInviteEmptyDescription": "Each friend who registers using your invite code gives you bonus credits",
   "settingsInviteInputLabel": "Enter invite code (optional)",
   "settingsInviteInputHint": "Enter code to bind your inviter",
-  "settingsInviteInvalidCode": "Please enter a valid 6-character invite code"
+  "settingsInviteInvalidCode": "Please enter a valid 6-character invite code",
+  "settingsDoNotSellTitle": "Personalized Ads",
+  "settingsDoNotSellDescription": "When off, your personal info won't be used for ad recommendations",
+  "settingsDoNotSellEnabled": "Off",
+  "settingsDoNotSellDisabled": "On"
 }

apps/lib/l10n/app_localizations.dart

@@ -2300,6 +2300,30 @@ abstract class AppLocalizations {
   /// In zh, this message translates to:
   /// **'请输入有效的6位邀请码'**
   String get settingsInviteInvalidCode;
+
+  /// No description provided for @settingsDoNotSellTitle.
+  ///
+  /// In zh, this message translates to:
+  /// **'个性化广告推荐'**
+  String get settingsDoNotSellTitle;
+
+  /// No description provided for @settingsDoNotSellDescription.
+  ///
+  /// In zh, this message translates to:
+  /// **'关闭后，我们不会将您的个人信息用于广告推荐'**
+  String get settingsDoNotSellDescription;
+
+  /// No description provided for @settingsDoNotSellEnabled.
+  ///
+  /// In zh, this message translates to:
+  /// **'已关闭'**
+  String get settingsDoNotSellEnabled;
+
+  /// No description provided for @settingsDoNotSellDisabled.
+  ///
+  /// In zh, this message translates to:
+  /// **'已开启'**
+  String get settingsDoNotSellDisabled;
 }
 
 class _AppLocalizationsDelegate

apps/lib/l10n/app_localizations_en.dart

@@ -1211,4 +1211,17 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get settingsInviteInvalidCode =>
       'Please enter a valid 6-character invite code';
+
+  @override
+  String get settingsDoNotSellTitle => 'Personalized Ads';
+
+  @override
+  String get settingsDoNotSellDescription =>
+      'When off, your personal info won\'t be used for ad recommendations';
+
+  @override
+  String get settingsDoNotSellEnabled => 'Off';
+
+  @override
+  String get settingsDoNotSellDisabled => 'On';
 }

apps/lib/l10n/app_localizations_zh.dart

@@ -1159,6 +1159,18 @@ class AppLocalizationsZh extends AppLocalizations {
 
   @override
   String get settingsInviteInvalidCode => '请输入有效的6位邀请码';
+
+  @override
+  String get settingsDoNotSellTitle => '个性化广告推荐';
+
+  @override
+  String get settingsDoNotSellDescription => '关闭后，我们不会将您的个人信息用于广告推荐';
+
+  @override
+  String get settingsDoNotSellEnabled => '已关闭';
+
+  @override
+  String get settingsDoNotSellDisabled => '已开启';
 }
 
 /// The translations for Chinese, using the Han script (`zh_Hant`).
@@ -2072,4 +2084,16 @@ class AppLocalizationsZhHant extends AppLocalizationsZh {
 
   @override
   String get settingsInviteInvalidCode => '請輸入有效的6位邀請碼';
+
+  @override
+  String get settingsDoNotSellTitle => '個人化廣告推薦';
+
+  @override
+  String get settingsDoNotSellDescription => '關閉後，我們不會將您的個人資訊用於廣告推薦';
+
+  @override
+  String get settingsDoNotSellEnabled => '已關閉';
+
+  @override
+  String get settingsDoNotSellDisabled => '已開啟';
 }

apps/lib/l10n/app_zh.arb

@@ -483,5 +483,9 @@
   "settingsInviteEmptyDescription": "每成功邀请一位好友注册，您将获得积分奖励",
   "settingsInviteInputLabel": "输入邀请码（选填）",
   "settingsInviteInputHint": "输入邀请码绑定您的邀请人",
-  "settingsInviteInvalidCode": "请输入有效的6位邀请码"
+  "settingsInviteInvalidCode": "请输入有效的6位邀请码",
+  "settingsDoNotSellTitle": "个性化广告推荐",
+  "settingsDoNotSellDescription": "关闭后，我们不会将您的个人信息用于广告推荐",
+  "settingsDoNotSellEnabled": "已关闭",
+  "settingsDoNotSellDisabled": "已开启"
 }

apps/lib/l10n/app_zh_hant.arb

@@ -385,5 +385,9 @@
   "wuXingTu": "土",
   "wuXingJin": "金",
   "wuXingShui": "水",
-  "retry": "重試"
+  "retry": "重試",
+  "settingsDoNotSellTitle": "個人化廣告推薦",
+  "settingsDoNotSellDescription": "關閉後，我們不會將您的個人資訊用於廣告推薦",
+  "settingsDoNotSellEnabled": "已關閉",
+  "settingsDoNotSellDisabled": "已開啟"
 }