fix: nginx startup, kiosk fullscreen, reboot errors, kiosk toggle

- Remove hardcoded Tailscale IP from nginx listen (broke fresh install)
- Generate SSL cert in installer if rootfs missed it (safety net)
- Kiosk: add --start-fullscreen --start-maximized --window-size flags
- Kiosk: remove --disable-gpu (can prevent fullscreen rendering)
- Kiosk: add toggle command and Ctrl+Alt+F1/F7 docs in MOTD
- Reboot: suppress stderr during cleanup to hide flashing errors

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

image-recipe/configs/nginx-archipelago.conf

@@ -5,7 +5,6 @@ limit_req_zone $binary_remote_addr zone=peer:10m rate=10r/s;
 
 server {
     listen 80;
-    listen 100.91.10.103:80;
     server_name _;
 
     root /opt/archipelago/web-ui;