feat: add master password hint functionality

- Updated user model to include masterPasswordHint.
- Modified sync handler to return masterPasswordHint.
- Implemented password hint retrieval in public API.
- Enhanced user profile management to allow updating of password hint.
- Added UI components for displaying and editing password hint.
- Updated localization files for new password hint strings.
- Improved rate limiting for sensitive public requests.
- Adjusted database schema to accommodate master password hint.

src/config/limits.ts

@@ -44,6 +44,12 @@
     // Sensitive public/auth request budget per IP per minute.
     // 敏感公开/认证接口每 IP 每分钟请求配额。
     sensitivePublicRequestsPerMinute: 30,
+    // Password hint lookup budget per IP per minute.
+    // 密码提示查询接口每 IP 每分钟请求配额。
+    passwordHintRequestsPerMinute: 1,
+    // Password hint lookup budget per IP per hour.
+    // 密码提示查询接口每 IP 每小时请求配额。
+    passwordHintRequestsPerHour: 3,
     // Register endpoint budget per IP per minute.
     // 注册接口每 IP 每分钟请求配额。
     registerRequestsPerMinute: 5,