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>

tooling/render-nginx.sh

@@ -1,22 +1,21 @@
 #!/usr/bin/env bash
-# render-nginx.sh — render an nginx vhost template with the .env values.
+# render-nginx.sh — render the nginx vhost template with the .env values.
 #
-# Substitutes $BASE_DOMAIN, $APP_DIR, $CADDY_HTTP_PORT into a template and
-# prints the result to stdout, or installs it with --install (writes to
-# sites-available, symlinks sites-enabled, tests, reloads nginx).
+# Substitutes $BASE_DOMAIN, $APP_DIR, $CADDY_HTTP_PORT into
+# nginx/ulicraft-caddy.conf.tmpl (the host nginx that terminates TLS in front of
+# caddy) and prints the result to stdout, or installs it with --install (writes
+# to sites-available, symlinks sites-enabled, tests, reloads nginx).
 #
 # Usage:
-#   tooling/render-nginx.sh                 # render caddy-front template -> stdout
+#   tooling/render-nginx.sh                 # render -> stdout
 #   tooling/render-nginx.sh --install       # render + install + reload nginx
-#   TEMPLATE=nginx/ulicraft.conf.tmpl tooling/render-nginx.sh   # the static variant
 #
 # .env vars used:
 #   BASE_DOMAIN       required
-#   CADDY_HTTP_PORT   caddy-front template only (localhost port nginx proxies to)
+#   CADDY_HTTP_PORT   localhost port nginx reverse-proxies to (caddy)
 # optional:
 #   APP_DIR           host path to this repo (cert files live under APP_DIR/certs)
 #                     — defaults to the repo root (this checkout)
-#   TEMPLATE          template to render (default nginx/ulicraft-caddy.conf.tmpl)
 #   SITE_NAME         installed filename (default ulicraft.conf)
 set -euo pipefail