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/api/infra/base/rbac.yaml

@@ -2,7 +2,7 @@ apiVersion: rbac.authorization.k8s.io/v1
 kind: Role
 metadata:
   name: hightower-api
-  namespace: shannon
+  namespace: hightower
 rules:
   - apiGroups: ["batch"]
     resources: ["jobs"]
@@ -18,11 +18,11 @@ apiVersion: rbac.authorization.k8s.io/v1
 kind: RoleBinding
 metadata:
   name: hightower-api
-  namespace: shannon
+  namespace: hightower
 subjects:
   - kind: ServiceAccount
     name: hightower-api
-    namespace: shannon
+    namespace: hightower
 roleRef:
   kind: Role
   name: hightower-api