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>

nginx/ulicraft-caddy.conf.tmpl

@@ -1,19 +1,17 @@
 # ──────────────────────────────────────────────────────────────────
 # Ulicraft host nginx — TLS terminator in FRONT of caddy.
 # ──────────────────────────────────────────────────────────────────
-# Alternative to ulicraft.conf.tmpl. Instead of nginx serving the static
-# files + proxying only drasl, here caddy (the docker container) is the single
-# ingress for ALL vhosts and nginx just terminates TLS and reverse-proxies
-# everything to caddy by Host header.
+# caddy (in docker-compose.yml) is the single internal ingress for ALL vhosts;
+# this host nginx terminates TLS and reverse-proxies everything to caddy by Host
+# header. Prefer tooling/render-nginx.sh over hand-rendering.
 #
 # Caddy must be published on a localhost port — set in .env:
 #   CADDY_HTTP_PORT=8880
 #   CADDY_HTTP_BIND=127.0.0.1
-# and the stack brought up with the caddy override (NOT the nginx override):
-#   docker compose -f docker-compose.yml -f docker-compose.caddy.yml \
-#     -f docker-compose.static.yml up -d
+# and the stack brought up:
+#   docker compose up -d
 #
-# Render with BOTH vars then install:
+# Render with the vars then install:
 #   CADDY_HTTP_PORT=8880 BASE_DOMAIN=ulicraft.net APP_DIR=/home/ubuntu/mc/ulicraft-server-v1 \
 #     envsubst '$CADDY_HTTP_PORT $BASE_DOMAIN $APP_DIR' \
 #     < nginx/ulicraft-caddy.conf.tmpl | sudo tee /etc/nginx/sites-available/ulicraft.conf