- Add VideoProcessor service to PostHandler for frame-based video moderation
- Implement multi-frame extraction and Azure OpenAI Vision analysis for video content
- Enhance VideoStitchingService with filters, speed control, and text overlays
- Add image upload dialogs for group avatar and banner in GroupCreationModal
- Implement navigation placeholders for mentions, hashtags, and URLs in sojornRichText
- Add ALTCHA service with challenge generation and verification
- Update auth and admin handlers to use ALTCHA tokens
- Replace Turnstile widget with ALTCHA widget in Flutter app
- Update admin frontend to use ALTCHA token
- Add ALTCHA challenge endpoints for both auth and admin
- Maintain development bypass for testing
- Remove Turnstile dependencies from authentication flow
