refactor!: unify into one compose, drop airgap/mirror/dnsmasq/avahi/blessingskin

Collapse the override-file matrix into a single docker-compose.yml holding the
whole stack: drasl, minecraft, mc-backup, caddy, nmsr, uptime-kuma. Bring-up is
now just `docker compose up -d --build`.

Removed features (dead-ends for this deployment):
- airgap / full asset mirror (mirror-airgap.sh, mirror-mods.sh, 20-mirror.caddy,
  caddy local-CA export, /ca.crt)
- dnsmasq + avahi/mDNS + dns-records.sh + mdns-host-setup.sh + ENABLE_MDNS;
  DNS is now handled outside this repo (HOST_LAN_IP dropped)
- Blessing Skin auth variant (compose + 00-core-blessingskin.caddy + BS_* env)
- host-nginx-static variant (docker-compose.nginx.yml, nginx/ulicraft.conf.tmpl)
- build-stack.sh and its run modes (online/airgap/core)

Production ingress is the only path now: host nginx terminates TLS (LE certs)
in front of caddy on a localhost-only port; caddy routes every vhost by Host
header. Launcher downloads move mirror/launcher -> launcher/.

Docs: README, deploy skill, and plan/ rewritten to match; obsolete plan docs
(dnsmasq, blessing-skin, assets-mirror, full-airgap-mirror, dns-and-run-modes)
deleted.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

caddy/conf.d/10-static.caddy

@@ -1,13 +1,5 @@
-# Static toggle — apex landing page + launcher downloads.
-# Mounted only when the stack runs with static files (build-stack.sh up static|full).
+# Apex — landing page (/srv/www) + launcher downloads (/srv/launcher).
 http://{$BASE_DOMAIN} {
-	# Caddy's local CA root, so guests can trust the air-gap HTTPS mirror.
-	# Mounted from ./caddy/caddy-root-ca.crt (exported by build-stack prep;
-	# the live pki dir is root-only 0600 and can't be served directly).
-	handle /ca.crt {
-		root * /srv/ca-pub
-		file_server
-	}
 	# Launcher downloads are a sibling mount (/srv/launcher), not nested under
 	# the read-only /srv/www. handle_path strips the /launcher prefix.
 	handle_path /launcher/* {