Fix password change feature that was previously non-functional:
- Add changePassword function in frontend API (src/lib/api/users.ts)
- Update API endpoint to match backend: PATCH /api/v1/users/me/password
- Connect profile page to real API instead of mock implementation
- Export changePassword function from API index
The backend endpoint was already implemented but frontend was using
a placeholder Promise.resolve(). Now properly calls the backend API.
Refs: apps/frontend/app/dashboard/profile/page.tsx:87-105
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
