Add services/wordpress.sh — multi-site WordPress with shared MariaDB

New service: self-hosted WordPress, sized for running several
independent sites the way a hosting company would, not just one blog.

- Multi-site from the start: every site requires a name (no unnamed
  "first instance" special case like mattermost's — there's no
  backward-compat reason to special-case one here) and gets its own
  directory/container/port, but all sites share ONE MariaDB container
  (chain-installed on first site, reused by every other one) instead of
  a dedicated database container per site — same resource-sharing idea
  as services/coturn.sh, just scoped to WordPress's own sites rather
  than shared across different services. Each site gets its own
  database + user within that shared instance.
- E-commerce is just WooCommerce, a normal WordPress plugin — no
  separate infrastructure. PHP memory_limit/upload_max_filesize/
  post_max_size are pre-tuned (256M/64M/64M) so a product-catalog
  import doesn't hit default-image limits on the first try.
- wp-cli (official wordpress:cli image, run as a one-off container
  sharing the site's html volume) does the initial WordPress core
  install non-interactively — title, admin account — so there's no
  browser setup wizard to remember per site. Falls back to printing
  the exact manual command if the site wasn't ready in time.
- Auto-scans for a free host port per site (multiple sites can't all
  bind 8090), matching the "auto-scanned free ports for extras" idea
  already used by mattermost's multi-instance support.
- DB and admin passwords are reused across reruns (checked against the
  DB-password-regeneration bug class already fixed elsewhere in this
  repo, e.g. PR #265) — verified via a real update-mode rerun that the
  credential doesn't change.
- setup.sh: is_installed() gets a wordpress case — every site is named
  from the first one on, so there's never a plain $DOCKER_DIR/wordpress
  directory the default case could match against.
- README.md: added to the utilities services table + copiable list per
  CLAUDE.md's three-step rule for new services. Also fixed `coturn`
  being in the homelab row's prose but missing from the copiable list
  block below it — a pre-existing gap from when coturn.sh was merged.

Verified end-to-end via non-interactive dry runs against a fake docker
shim (no live daemon in this environment): 3 sites installed in
sequence get 3 distinct databases, 3 distinct auto-scanned ports, the
shared DB is only set up once, and an update-mode rerun preserves the
existing DB password rather than regenerating it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TBtExJcqxnokyZZKmphdug

README.md

@@ -68,7 +68,7 @@ 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` |
-| `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` |
+| `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, shared MariaDB — 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` |
@@ -89,6 +89,7 @@ homelab
   caddy
   crowdsec
   authelia
+  coturn
   homeassistant
   asterisk
   pstn-trunk
@@ -131,6 +132,7 @@ utilities
   watchyourlan
   watchtower
   wg-easy
+  wordpress
 
 media
   arm