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>

apps/longhorn.yaml

@@ -0,0 +1,36 @@
+# Longhorn — this repo's pre-installed storage layer. Same pattern as
+# apps/metallb.yaml: an Application pointing at a Helm chart
+# (apps/longhorn/) that pulls in the official upstream chart. Once this
+# syncs, any app in this cluster can request persistent storage (a
+# PersistentVolumeClaim) and actually get real, replicated storage backed
+# by the dedicated disk each node prepared in
+# talos/patch-longhorn.yaml — see docs/06-longhorn.md.
+#
+# Longhorn needs privileged Pods (it manages block devices directly) and
+# the `open-iscsi`/`util-linux-tools` Talos system extensions baked into
+# your node image — both covered in docs/01-prerequisites.md and
+# docs/02-talos-bootstrap.md. Skipping either means Longhorn's Pods will
+# sit unhealthy no matter how correctly this Application syncs.
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: longhorn
+  namespace: argocd
+spec:
+  project: default
+
+  source:
+    repoURL: https://github.com/YOUR_GITHUB_USERNAME/k8s-starter-pack.git
+    targetRevision: main
+    path: apps/longhorn
+
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: longhorn-system
+
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+    syncOptions:
+      - CreateNamespace=true