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>

docker/avahi/Dockerfile

@@ -1,9 +0,0 @@
-# Publishes the stack's service names on .local via the HOST's avahi-daemon
-# (over its D-Bus socket — no second daemon, avoids the :5353 collision).
-# Requires the host to run avahi-daemon and the socket to be mounted (see
-# docker-compose.avahi.yml). Used when ENABLE_MDNS=true and BASE_DOMAIN=*.local.
-FROM alpine:3.20
-RUN apk add --no-cache avahi-tools
-COPY entrypoint.sh /entrypoint.sh
-RUN chmod +x /entrypoint.sh
-ENTRYPOINT ["/entrypoint.sh"]

docker/avahi/entrypoint.sh

@@ -1,32 +0,0 @@
-#!/bin/sh
-# Publish A records for the stack's service names on .local via the HOST's
-# avahi-daemon (reached over its mounted D-Bus socket). One avahi-publish per
-# name; if any drops the container exits so Docker restarts it.
-set -eu
-
-: "${BASE_DOMAIN:?BASE_DOMAIN unset}"
-: "${HOST_LAN_IP:?HOST_LAN_IP unset}"
-
-case "$BASE_DOMAIN" in
-  *.local) ;;
-  *) echo "WARN: mDNS resolves only .local — BASE_DOMAIN=$BASE_DOMAIN will NOT be discoverable via avahi. Set BASE_DOMAIN=*.local to use mDNS." >&2 ;;
-esac
-
-bus="${DBUS_SYSTEM_BUS_ADDRESS:-unix:path=/run/dbus/system_bus_socket}"
-sock=${bus#unix:path=}
-if [ ! -S "$sock" ]; then
-  echo "ERROR: host D-Bus socket '$sock' not found. Mount the host's" >&2
-  echo "       /run/dbus/system_bus_socket and ensure avahi-daemon runs on the host." >&2
-  exit 1
-fi
-export DBUS_SYSTEM_BUS_ADDRESS="$bus"
-
-pids=""
-for n in "$BASE_DOMAIN" "auth.$BASE_DOMAIN" "packwiz.$BASE_DOMAIN" "mc.$BASE_DOMAIN"; do
-  echo "mDNS publish (host avahi): $n -> $HOST_LAN_IP"
-  avahi-publish -a "$n" "$HOST_LAN_IP" &
-  pids="$pids $!"
-done
-
-# shellcheck disable=SC2086
-wait -n $pids 2>/dev/null || wait