Support multiple authentication options (GitHub, Google, Username-only) #32
Description
Summary:
Introduce flexible authentication to allow users to sign in or register via GitHub OAuth, Google OAuth, or traditional username/password (with optional email).
Acceptance Criteria:
- Add "Sign in with GitHub" and "Sign in with Google" (OAuth-based) as authentication options.
- Update traditional registration flow: make email optional with a clear warning if omitted ("no password recovery if email not provided").
- Provide clear UI to communicate risks/options.
- Ensure users can manage accounts with minimum liability for email/PPI.
- Keep Django admin only accessible via direct URL, hidden from main app navigation.
Rationale:
- Improves user privacy and choice.
- Reduces password/data breach liability for operators.
- Matches best practices in modern authentication experiences.
Label: enhancement