refactor: rename all custom K8s components to hightower

Namespace, Temporal, router, PVCs, labels, and GHCR API image all
renamed from shannon-* to hightower-*. Upstream references preserved:
worker image (ghcr.io/farhoodliquor/shannon), .shannon/ dirs,
@shannon/worker package imports.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/cli/infra/k8s/namespace.yaml

@@ -1,6 +1,6 @@
 apiVersion: v1
 kind: Namespace
 metadata:
-  name: shannon
+  name: hightower
   labels:
-    app.kubernetes.io/part-of: shannon
+    app.kubernetes.io/part-of: hightower