feat(auth): add Okta OAuth support and auth configuration enhancements

[Aveerayy]

Summary

Adds Okta as a social authentication provider with additional auth configuration improvements.

Changes

• ✅ Okta OAuth support with OKTA_ISSUER configuration
• ✅ Google/Microsoft force account selection flags (*_FORCE_ACCOUNT_SELECTION)
• ✅ Respect DISABLE_EMAIL_SIGN_IN and DISABLE_SIGN_UP environment variables
• ✅ Enhanced OAuth documentation with setup guides
• ✅ Secret tainting for improved security

Environment Variables Added

OKTA_CLIENT_ID=your_okta_client_id
OKTA_CLIENT_SECRET=your_okta_client_secret
OKTA_ISSUER=https://your-okta-domain/oauth2/default
GOOGLE_FORCE_ACCOUNT_SELECTION=1
MICROSOFT_FORCE_ACCOUNT_SELECTION=1
DISABLE_EMAIL_SIGN_IN=1
DISABLE_SIGN_UP=1

Testing

• Local build successful
• TypeScript checks pass
• UI components render correctly

[vercel]

@Aveerayy is attempting to deploy a commit to the cgoinglove's projects Team on Vercel.

A member of the Team first needs to authorize it.

[brrock]

Thank you, this is much cleaner implementation, could you add MCP auth with okta?

[Aveerayy]

@brrock thanks for the wait. I included user authN with okta for MCP servers in this PR #359, please review