Authentication & Login UI

[vivjd]

Goal:
Create the frontend login experience for admins and volunteers.

Tasks:

• Login page with email/password fields
• POST /api/auth/login → store JWT or session token
• Redirect based on role (ADMIN → dashboard, VOLUNTEER → home)
• Logout clears token and redirects to login

Acceptance Criteria:

• Valid login grants access to protected pages
• Invalid credentials show an error
• Session persists safely and clears on logout