main ← voice-media-group-gating
Previously, camera video and screen sharing shared a single site-wide `voice_vid…eo_enabled` boolean, so a site could only enable or disable both for everybody at once.
This change replaces it with `voice_video_allowed_groups` and `voice_screen_share_allowed_groups` (empty list = off), resolving each capability per user against the room's own `video_enabled` flag and their speaking rights, and enforcing it at the participant state endpoint and in LiveKit's per-source publish grants.