- Add client-side form for cycleLength, notificationTime, timezone - Fetch user data on mount and pre-fill form values - Submit updates via PATCH /api/user with loading states - Display success/error messages with proper accessibility - Clear messages when user modifies form - 24 tests covering rendering, data loading, validation, error handling Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>