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

.trellis/tasks/04-17-feat-privacy-do-not-sell/task.json

@@ -0,0 +1,31 @@
+{
+  "name": "feat-privacy-do-not-sell",
+  "title": "Do Not Sell My Personal Information 开关",
+  "dev_type": "fullstack",
+  "created_at": "2026-04-17",
+  "status": "in_progress",
+  "worktree": "feat-privacy-do-not-sell",
+  "description": "实现 CCPA/CPRA 合规的 Do Not Sell My Personal Information 开关功能：将 privacy 字段升级为结构化 PrivacySettings 对象，主开关在隐私通知设置页，法律中心列表页提供快捷入口，后端存储用户偏好，默认开启（不卖）。",
+  "prd": "prd.md",
+  "related_docs": [
+    "docs/discussions/legal-compliance-us.md",
+    "https://uidqlzahr8w.feishu.cn/wiki/As6AwJRImilu4Lk0lNtcrbmXnOc"
+  ],
+  "checklist": {
+    "backend": [
+      "Create PrivacySettings class with do_not_sell + future fields",
+      "Update ProfileSettingsV1.privacy to use PrivacySettings type",
+      "Add backward compatibility logic for existing dict data",
+      "Verify PATCH /users/me/settings works with new PrivacySettings"
+    ],
+    "frontend": [
+      "Create PrivacySettings class matching backend schema",
+      "Update ProfileSettingsV1.privacy to use PrivacySettings type",
+      "Add SettingsSwitchTile to PrivacyNotificationSettingsScreen (main switch)",
+      "Keep Profile Visibility placeholder unchanged",
+      "Add SettingsMenuTile shortcut to LegalCenterScreen (CCPA compliance)",
+      "Implement navigation from LegalCenter to PrivacyNotificationSettings",
+      "Add l10n keys (zh/en/zh_Hant): title, description, enabled, disabled"
+    ]
+  }
+}