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/features/settings/data/models/profile_settings.dart

@@ -84,6 +84,23 @@ class DivinationTutorialSettings {
   }
 }
 
+class PrivacySettings {
+  const PrivacySettings({
+    this.canSell = false,
+    this.profileVisibility = 'public',
+  });
+
+  final bool canSell;
+  final String profileVisibility;
+
+  PrivacySettings copyWith({bool? canSell, String? profileVisibility}) {
+    return PrivacySettings(
+      canSell: canSell ?? this.canSell,
+      profileVisibility: profileVisibility ?? this.profileVisibility,
+    );
+  }
+}
+
 class ProfileSettingsV1 {
   const ProfileSettingsV1({
     this.version = 1,
@@ -92,7 +109,7 @@ class ProfileSettingsV1 {
     this.avatarPath,
     this.avatarUrl,
     this.preferences = const PreferenceSettings(),
-    this.privacy = const <String, Object?>{},
+    this.privacy = const PrivacySettings(),
     this.notification = const NotificationSettings(),
     this.divinationTutorial = const DivinationTutorialSettings(),
   });
@@ -103,7 +120,7 @@ class ProfileSettingsV1 {
   final String? avatarPath;
   final String? avatarUrl;
   final PreferenceSettings preferences;
-  final Map<String, Object?> privacy;
+  final PrivacySettings privacy;
   final NotificationSettings notification;
   final DivinationTutorialSettings divinationTutorial;
 
@@ -114,7 +131,7 @@ class ProfileSettingsV1 {
     String? avatarPath,
     String? avatarUrl,
     PreferenceSettings? preferences,
-    Map<String, Object?>? privacy,
+    PrivacySettings? privacy,
     NotificationSettings? notification,
     DivinationTutorialSettings? divinationTutorial,
   }) {