[auth]: profile page #487

Depends on #485

Description

Add a basic profile page so logged-in users can view their account information and change their password.

Djoser already provides the endpoints for this: /api/auth/users/me/ for viewing account info and /api/auth/users/set_password/ for changing password. The work is building the frontend page and adding a link to it in the header for logged-in users.

Acceptance criteria:

• Logged-in user can view their name and email on the profile page
• Logged-in user can change their password
• Profile page is not accessible to unauthenticated users
• Header has a link to the profile page when logged in