Replace password auth with OAuth

[gsiener]

Problem

Storing Google password in environment variables is insecure and doesn't support 2FA accounts.

Proposed Solution

Implement proper OAuth flow for the browser automation account:

1. User authorizes once via OAuth consent screen
2. Store refresh token securely
3. Auto-refresh access tokens

Technical Considerations

• Need OAuth client credentials
• Secure token storage (encrypted file or keychain)
• Handle token refresh
• Support for multiple Google accounts?

Security

This is important for production use. Current password approach is prototype-only.