Move to a three-node cluster with a Talos VIP; add Longhorn

Every node is now both control plane and worker, giving real tolerance
for losing any single machine (etcd quorum needs 3, not 1). A Talos VIP
gives the cluster one stable address regardless of which node answers.

Also pre-installs Longhorn for replicated storage, backed by a Talos
UserVolume on each node's second disk (>=900GB, non-system) rather than
the default path — mirroring the pattern from the homescale repo.

Docs renumbered to make room for 06-longhorn.md; checklist, glossary,
network map, and CLAUDE.md's guided-bootstrap instructions updated to
match, including asking the user for node IPs, VIP, and disk info before
generating any Talos config.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

argocd/README.md

@@ -105,8 +105,8 @@ argocd app get app-of-apps
 argocd app list
 ```
 
-You should see `app-of-apps` sync, then `demo` and `metallb` Applications
-appear underneath it, then sync themselves. See
+You should see `app-of-apps` sync, then `demo`, `metallb`, and `longhorn`
+Applications appear underneath it, then sync themselves. See
 [`docs/04-app-of-apps.md`](../docs/04-app-of-apps.md) for what's happening
 here and [`docs/checklist.md`](../docs/checklist.md) for the full guided
 path.