docs(plan): scrub stale pack subdomain + packwiz from live-arch docs

The pack./packwiz service was removed operationally long ago, but several
plan docs still presented pack. as a live caddy vhost / DNS subdomain and
render-pack.sh as a current tool. Remove those references from the
current-architecture docs (overview, caddy, tooling, uptime-kuma,
letsencrypt, mc-backup); leave the migration log (04-mods.md), superseded
banner (04-packwiz.md), commit history (12-build-order.md), and planned
landing rework (18) intact as deliberate history.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plan/15-letsencrypt.md

@@ -9,7 +9,7 @@ path — there are no compose overrides.
 ## Certs: one per name, via OVH DNS-01
 
 `tooling/issue-letsencrypt.sh` issues a **separate** cert for the apex and each
-subdomain (`${BASE_DOMAIN}`, `auth.…`, `pack.…`, plus the rest of
+subdomain (`${BASE_DOMAIN}`, `auth.…`, plus the rest of
 `LE_SUBDOMAINS`) using acme.sh + the OVH DNS-01 challenge — no inbound ports
 needed, so it works regardless of public reachability.
 
@@ -55,7 +55,7 @@ the reload with `RELOAD_CMD=...` if nginx isn't systemd-managed.
 ## DNS
 
 Point the public DNS for `${BASE_DOMAIN}` and every subdomain
-(`auth.` `pack.` `avatar.` `status.` `distribution.` `www.`) at the host running
+(`auth.` `avatar.` `status.` `distribution.` `www.`) at the host running
 nginx. DNS is configured **outside this repo**. The Minecraft container reaches
 the stack's own names via caddy's `mcnet` aliases, not public DNS.