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/types/index.ts

@@ -35,6 +35,7 @@ export interface User {
   id: string;
   email: string;
   name: string | null;
+  masterPasswordHint: string | null;
   masterPasswordHash: string;
   key: string;
   privateKey: string | null;