chore(uptime-kuma): bump image to :2

The :1 image runs Node 18 (EOL), which gets no fix for the October 2026
Node.js security release. :2 migrates kuma.db in place on first start;
back up kuma_data per host before pulling (see plan/10-uptime-kuma.md).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plan/10-uptime-kuma.md

@@ -5,13 +5,13 @@
 > card. Both ping `minecraft` over `mcnet` but serve different purposes.
 
 Status monitoring + public status page. Service `uptime-kuma`
-(`louislam/uptime-kuma:1`), web UI on `:3001`, reached only through caddy at
+(`louislam/uptime-kuma:2`), web UI on `:3001`, reached only through caddy at
 `https://status.${BASE_DOMAIN}`. Joined to `mcnet`, so it can probe every other
 service by its internal container name.
 
 ## Add a Minecraft monitor
 
-Uptime Kuma 1.x ships a built-in **Minecraft Server** monitor type. It uses the
+Uptime Kuma ships a built-in **Minecraft Server** monitor type. It uses the
 Server List Ping protocol (the same ping the vanilla multiplayer list uses):
 unauthenticated, so it works fine with `ONLINE_MODE=FALSE` /
 `ENFORCE_SECURE_PROFILE=FALSE`. It reports latency, online/max players, and MOTD.
@@ -53,6 +53,12 @@ monitor stays green. Run both to tell *server down* apart from *path broken*.
   `https://auth.${BASE_DOMAIN}`, `https://distribution.${BASE_DOMAIN}`,
   `https://${BASE_DOMAIN}`, `https://files.${BASE_DOMAIN}` — a red
   `distribution.` here explains client mod-mismatch join failures.
+- **1 → 2 upgrade (2026-10-25)** — moved off `:1`, whose image runs Node 18
+  (EOL, no fix for the Oct 2026 Node CVEs). The first `:2` start migrates
+  `kuma.db` in place (one-way, minutes on a ~140M DB; status page down until it
+  finishes — don't interrupt). Per host: `docker compose stop uptime-kuma`, tar
+  the `kuma_data` volume into `./backups/`, then `pull` + `up -d uptime-kuma`.
+  Rollback = restore the tarball + revert the tag to `:1`.
 
 > **An HTTP monitor cannot see an SPA break.** It asserts "the server returned
 > 200", which is a much weaker claim than "the app works". `files.` (Filestash)