Add Basic Auth Support

[JustinMissmahl]

Adds username/password authentication mode for self-hosted instances that want to manage users manually without OAuth providers.

Changes:

Backend:

• basic_auth.py: Login endpoint and metadata endpoint returning {"google": null}
• state.py: Added controlled_access_mode flag
• main.py: CLI flag and env var handling
• configure.py: Router mounting and auth middleware

Frontend (loginPrompt.tsx):

• Basic auth detection from metadata response
• Username/password form with loading/error states
• Works in both mobile/desktop views
• Preserves existing OAuth/email flows

Usage:

1. Enable controlled access mode via:

   • CLI: --controlled-access
   • ENV: KHOJ_CONTROLLED_ACCESS=true

2. Initial admin credentials:

   • Username: [email protected]
   • Password: admin

3. Managing Users:

   • Login as admin at http://localhost:42110/server/admin
   • Use Django admin interface to:
     • Create new users
     • Set passwords * Manage permissions
   • Users can then login with their credentials at http://localhost:42110

Security Notes:

• Default admin should be changed after first login
• Each user needs to be manually created by admin
• No self-registration - controlled environment

Testing:

docker compose up  # Uses KHOJ_CONTROLLED_ACCESS=true

1. Visit http://localhost:42110 - should show username/password form
2. Login with admin credentials
3. Create test user in admin panel
4. Test login with new user