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-config.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # render-config.sh — turn *.tmpl files into real configs via envsubst.
-# Substitutes ONLY ${BASE_DOMAIN} and ${HOST_LAN_IP} so literal $-syntax that
-# belongs to the target file (dnsmasq, caddy, toml) is left untouched.
+# Substitutes ONLY ${BASE_DOMAIN} so literal $-syntax that belongs to the target
+# file (caddy, toml) is left untouched.
 # Halts on any unset var or missing template (cautious: no half-rendered output).
 set -euo pipefail
 
@@ -9,17 +9,15 @@ cd "$(dirname "$0")/.."   # repo root
 
 [ -f .env ] && { set -a; . ./.env; set +a; }
 : "${BASE_DOMAIN:?BASE_DOMAIN unset (set in .env)}"
-: "${HOST_LAN_IP:?HOST_LAN_IP unset (set in .env)}"
 
 render() {  # $1=template  $2=output
   [ -f "$1" ] || { echo "missing template: $1" >&2; exit 1; }
-  envsubst '${BASE_DOMAIN} ${HOST_LAN_IP}' < "$1" > "$2"
+  envsubst '${BASE_DOMAIN}' < "$1" > "$2"
   echo "rendered $2"
 }
 
 render drasl/config/config.toml.tmpl drasl/config/config.toml
 render nmsr/config.toml.tmpl          nmsr/config.toml
-render dnsmasq/dnsmasq.conf.tmpl      dnsmasq/dnsmasq.conf
 
 # pack templates (mods/*.pw.toml.tmpl, CustomSkinLoader, …) + packwiz index.
 # Delegated to render-pack.sh (BASE_DOMAIN only — single source of pack render).