W1: Cilium 1.16.5->1.17.18, Longhorn 1.7->1.8 (pre-k8s-1.32 component landing)

Land the two pacing components on current k8s 1.31 before the 1.32 k3s hop.
Cilium 1.17 supports k8s 1.29-1.32; Longhorn 1.8 supports 1.25+; Gateway API CRDs
stay v1.2.1 (Cilium 1.17 targets v1.2.x). Also commits the full upgrade plan doc.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

platform/cilium/helmrelease.yaml

@@ -27,7 +27,7 @@ spec:
       chart: cilium
       # [parity] Pinned to the exact version the Ansible bootstrap installs
       # (cilium_version in roles/cilium/defaults/main.yml). Renovate bumps both together.
-      version: "1.16.5"
+      version: "1.17.18"
       sourceRef:
         kind: HelmRepository
         name: cilium

platform/longhorn/helmrelease.yaml

@@ -14,7 +14,7 @@ spec:
   chart:
     spec:
       chart: longhorn
-      version: ">=1.7.0 <1.8.0"   # TODO(WS-STORAGE): pin at bring-up; Renovate maintains
+      version: ">=1.8.0 <1.9.0"   # W1 upgrade 1.7->1.8 (resolves 1.8.2; avoid buggy 1.8.0). Renovate maintains
       sourceRef:
         kind: HelmRepository
         name: longhorn