sky-cam: retire motionEye via direct RTSP capture, drop Frigate detour

capture.sh already replaces motionEye/any NVR itself - it just needs
each camera's RTSP URL. services/sky-cam.sh never actually prompted for
CAM_RTSP_<cam>, so capture/audio never had anything to connect to.

- Prompt per camera for its RTSP URL -> CAM_RTSP_<cam> in .env
- Prompt for sunrise mic / optional ambient audio library
- Fix Mattermost integration: sunrise2mm.py reads mattermost_url/
  access_token/channel_id (bot-token REST upload), not the
  MM_WEBHOOK_URL/MM_CHANNEL incoming-webhook scheme the installer used
  to write - uploads never worked before this
- Add optional ntfy push notifications
- Auto-generate SCHEDULE_SEASONS_<cam> (staggered 30 min apart) for
  every configured camera, not just the stock east/north/south, so
  install.sh wires up every applicable systemd timer for any camera set

Removes services/sky-cam-frigate.sh entirely - routing sky-cam's frames
through Frigate (via export API or restream) turned out to be solving a
problem that doesn't exist; sky-cam's own capture.sh talking directly to
each camera is simpler and has no quality/resolution tradeoffs. Frigate
continues to run fully independently for NVR/detection.

setup.sh

@@ -87,7 +87,6 @@ is_installed() {
         silent-send) [ -d "$ACTUAL_HOME/silent-send/.git" ] ;;
         sync-cc) [ -f "$ACTUAL_HOME/sync-cc/sync_cc.py" ] ;;
         sky-cam) [ -d "$ACTUAL_HOME/sky-cam/.git" ] ;;
-        sky-cam-frigate) [ -d "$ACTUAL_HOME/sky-cam/.git" ] && [ -f "$ACTUAL_HOME/sky-cam/frigate-retime.sh" ] ;;
         *) [ -e "$DOCKER_DIR/$1" ] ;;
     esac
 }