- Fixed duplicate authentication area in providers dashboard
- Restored full OAuth authentication with popup windows for all providers
- Added missing JavaScript authentication functions (authenticateClaude, authenticateQwen, authenticateCodex, authenticateKilo)
- Added missing backend endpoint /dashboard/providers/{provider_name}/auth/check
- Fixed import errors and attribute access for OAuth provider configs
- Fixed credential structure access for each OAuth provider type
- Fixed polling status responses (approved -> completed)
- Added human-readable expiration time formatting (days, hours, minutes, seconds)
- All OAuth flows now work with proper popup windows, polling, and status updates