feat(env): tokenize hardcoded dev LAN addresses into cluster-vars (R-ENV-02)

R-ENV-02 promises dev and prod differ ONLY by scoped cluster-vars overrides. In fact
dev LAN addresses were hardcoded into base manifests, so clusters/prod would have come
up ANNOUNCING DEV ADDRESSES (192.168.1.x) on the prod LAN (192.168.2.x).

New cluster-vars knobs (base default = dev literal, per the file's existing convention):
  K3S_API_HOST          platform/cilium/helmrelease.yaml (+ the values.yaml mirror)
  CILIUM_LB_POOL_START  platform-config/cilium/l2-ip-pool.yaml
  CILIUM_LB_POOL_STOP   "
  UNIFI_L4_VIP          apps/vms/unifi/50-service-l4.yaml
  CRAFTY_L4_VIP         platform/crafty/service-l4.yaml
  S3_BACKUP_ENDPOINT    platform/keycloak/postgres-cluster.yaml, apps/wave-0/{nextcloud,
                        semaphore}-db.yaml, and platform/velero/helmrelease.yaml

Also fixes GATEWAY_VIP's base default, which was still the RETIRED libvirt address
10.73.0.240, and adds the GATEWAY_VIP patch that clusters/prod was missing entirely.

clusters/base/apps-vms.yaml gains postBuild.substituteFrom (it was the one consuming
Kustomization without it, so a ${TOKEN} there would have shipped as a literal string).
The envsubst contract is documented there: ${VAR} substitutes and escapes as $${VAR};
$VAR and $(cmd) are left alone; ${ARR[0]} hard-errors. The three UOS_URL expansions in
the unifi cloud-init are escaped accordingly.

PROD ADDRESS PLAN (operator, 2026-08-31):
  nodes .10/.11/.12 · control-plane VIP .9 (Ansible-side) · GATEWAY_VIP .20
  Cilium LB pool .20-.30

CONTAINMENT INVARIANT, now documented at the pool and in the prod overlay: GATEWAY_VIP
MUST equal CILIUM_LB_POOL_START. The shared Gateway pins no address, so Cilium LB-IPAM
gives it the first free address of a matching pool block. An initial prod proposal put
.20 outside a .21-.30 pool; the Gateway would have come up on .21 while split-horizon
coredns-custom kept answering *.home.keithjackson.dev with .20 — an address nothing
announces — blackholing in-cluster OIDC hairpin traffic while reporting healthy. The
pool was widened to .20-.30. The control-plane VIP (.9) stays outside the pool so
kube-vip and LB-IPAM can never contend.

Values prod still cannot know stay INVALID `TBD-PROD-*` placeholders on purpose: base
defaults are dev values, so an omitted patch means prod silently inherits a dev address
— far worse than a loud failed apply.

DEV IS BYTE-IDENTICAL. Verified by kustomize build over 13 paths before/after, then
flux envsubst with the dev cluster-vars values applied to both sides: zero drift. The
only deltas are the intended additive keys in the overlay ConfigMap itself. No
unresolved ${TOKEN} survives. render-golden green (10 goldens); yamllint clean.

Serves: R-ENV-02. Task: T-7.1 (prerequisite). Gate: MERGE GATE: PASS.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

platform/crafty/service-l4.yaml

@@ -6,7 +6,8 @@
 # the crafty pod's network namespace. The Gateway API `shared` Gateway is an L7 HTTPS terminator and
 # CANNOT express raw TCP on arbitrary ports or UDP at all. So the game ports are exposed as
 # type=LoadBalancer Services whose VIP is pulled from the CiliumLoadBalancerIPPool `default-pool`
-# (192.168.1.53-.60) and ARP-announced on the flat LAN by the existing CiliumL2AnnouncementPolicy
+# (dev 192.168.1.53-.60; see CILIUM_LB_POOL_* in cluster-vars) and ARP-announced on the flat LAN by
+# the existing CiliumL2AnnouncementPolicy
 # `default-l2` (platform-config/cilium/*) — the SAME machinery the Gateway VIP and unifi already use.
 # No new Cilium config is needed; these Services just consume the pool.
 #
@@ -15,8 +16,9 @@
 # control plane) is Keycloak-gated (via the oauth2-proxy sidecar); the game ports carry player traffic
 # and must reach the server subprocesses directly.
 #
-# VIP: 192.168.1.55 — the next free address in default-pool (.53 = shared Gateway, .54 = unifi;
-# verified free live 2026-08-28). PINNED via lbipam.cilium.io/ips so players have a stable target.
+# VIP: CRAFTY_L4_VIP (cluster-vars, R-ENV-02; dev 192.168.1.55) — the next free address in
+# default-pool (dev: .53 = shared Gateway, .54 = unifi; verified free live 2026-08-28). PINNED via
+# lbipam.cilium.io/ips so players have a stable target. The `crafty` Flux Kustomization substitutes it.
 # ONE VIP, TWO SERVICES: a LoadBalancer Service is single-protocol-friendly, so TCP and UDP split into
 # two Services sharing the IP via lbipam.cilium.io/sharing-key (same pattern as unifi).
 #
@@ -38,8 +40,8 @@ metadata:
     app.kubernetes.io/name: crafty
   annotations:
     lbipam.cilium.io/sharing-key: "crafty"
-    lbipam.cilium.io/ips: "192.168.1.55"
-    # external-dns publishes A crafty-mc.home.keithjackson.dev -> 192.168.1.55 (the Java server target).
+    lbipam.cilium.io/ips: "${CRAFTY_L4_VIP}"
+    # external-dns publishes A crafty-mc.home.keithjackson.dev -> the pinned VIP (Java server target).
     external-dns.alpha.kubernetes.io/hostname: "crafty-mc.home.keithjackson.dev"
 spec:
   type: LoadBalancer
@@ -60,7 +62,7 @@ metadata:
     app.kubernetes.io/name: crafty
   annotations:
     lbipam.cilium.io/sharing-key: "crafty"    # same key + same IP => shares the VIP with -tcp
-    lbipam.cilium.io/ips: "192.168.1.55"
+    lbipam.cilium.io/ips: "${CRAFTY_L4_VIP}"
 spec:
   type: LoadBalancer
   externalTrafficPolicy: Local