Add Beszel for lightweight server + Docker monitoring

Answers "what's the best way to see CPU/RAM/disk usage on this box"
(IONOS's own dashboard doesn't expose it) and "does Gatus cover this" —
it doesn't, Gatus is a black-box HTTP check (is the site responding
from the outside), Beszel is white-box host/process monitoring (is the
box under memory/disk pressure, is a container actually running vs.
crash-looping). Complements Gatus rather than replacing it.

Mirrors the hub+agent same-system layout from beszel's own
supplemental/docker/same-system/docker-compose.yml (fetched from the
actual upstream repo, not reconstructed from memory) — hub is the web
dashboard, agent reads /var/run/docker.sock (read-only) to report every
currently-running container automatically, no per-service config
needed as containers get added or removed.

Genuinely a two-phase install: the hub's SSH keypair and universal
token only exist after logging into its web UI once, so this starts
the hub, walks through where to find both values, and finishes wiring
the agent once provided — skipping is fine, a rerun in "update" mode
detects the agent was never connected and offers to finish it.

Verified the generated docker-compose.yml/.env by running the actual
file-writing code path with docker/configure_caddy_for_service mocked
out — confirmed TOKEN/KEY are correctly left as literal
${AGENT_TOKEN:-}/${AGENT_KEY:-} for Docker Compose's own substitution
at "up" time, not prematurely expanded by the heredoc itself.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H4k6J1qXXyYxhGEgnJaMvn

README.md

@@ -168,7 +168,7 @@ a ready-to-copy Caddy config snippet to `~/docker/caddy-snippets/`.
 |-------|---------|
 | `base` | `net-tools`, `ncdu`, `git`, `curl`, `wget`, `htop`, `tree`, `zip`/`unzip`, `ca-certificates`, `gnupg`, `jq`, `rsync`; `glow` (terminal markdown reader, Charm apt repo); Docker CE + Compose plugin; `openssh-server` with GitHub/Launchpad SSH key import, optional password-auth lockdown, and SSH Host aliases; optional NetBird overlay network |
 | `homelab` | `caddy`, `crowdsec`, `authelia`, `coturn` (shared TURN/STUN relay — Asterisk, Mattermost Calls, and future WebRTC-capable services all register a dedicated credential against one instance instead of each running its own), `homeassistant`, `asterisk`, `pstn-trunk`, `sms-inbound`, `security-dashboard`, `sunshine`, `vpn-data-mount` (mount existing SMB shares from a NetBird-connected home box — SSH trust bootstrap, then read-only discovery of shares already configured there; never writes to the home box's Samba config; repeatable, pick from any number of a home box's shares in one pass; optional per-share [gocryptfs decrypt layer](#client-side-encryption-for-vpn-data-mount) so the VPS only ever handles ciphertext) |
-| `utilities` | `actualbudget`, `ai-gpu`, `ai-stack`, `archivebox`, `changedetection`, `ddclient`, `filebrowser`, `fmd`, `gatus`, `homebox`, `iopaint`, `joplin`, `koha`, `magicmirror`, `mail-archiver`, `mattermost`, `mealie`, `meshcentral`, `n8n`, `nextcloud`, `ntfy`, `onlyoffice`, `paintplus`, `portainer`, `rustdesk`, `stirling-pdf`, `syncthing`, `traccar`, `unifi`, `uptimekuma`, `vaultwarden`, `watchyourlan`, `watchtower`, `wg-easy`, `wordpress` (multi-site, dedicated MariaDB per site — blogs, business sites, e-commerce via WooCommerce) |
+| `utilities` | `actualbudget`, `ai-gpu`, `ai-stack`, `archivebox`, `beszel` (lightweight server + Docker monitoring — CPU/RAM/disk/network, auto-discovers running containers via the Docker socket; complements Gatus rather than replacing it — Gatus is a black-box HTTP check, Beszel is white-box host/process monitoring), `changedetection`, `ddclient`, `filebrowser`, `fmd`, `gatus`, `homebox`, `iopaint`, `joplin`, `koha`, `magicmirror`, `mail-archiver`, `mattermost`, `mealie`, `meshcentral`, `n8n`, `nextcloud`, `ntfy`, `onlyoffice`, `paintplus`, `portainer`, `rustdesk`, `stirling-pdf`, `syncthing`, `traccar`, `unifi`, `uptimekuma`, `vaultwarden`, `watchyourlan`, `watchtower`, `wg-easy`, `wordpress` (multi-site, dedicated MariaDB per site — blogs, business sites, e-commerce via WooCommerce) |
 | `media` | `arm`, `audiobookshelf`, `calibre-web`, `emby`, `immich`, `jellyfin`, `lyrion` |
 | `cameras` | `frigate`, `frigate-audio`, `frigate-notify`, `sky-cam` |
 | `gaming` | `drum-rhythm-game`, `js99er`, `kyber-launcher`, `kyber-server`, `minecraft`, `wolf`, `wolf-pair` |