refactor: rename custom components from shannon-* to hightower-*

Renames API server, worker jobs, credentials secret, and workspaces
PVC to use the hightower prefix. Upstream Shannon names (namespace,
Temporal service, package imports, .shannon/ dir) are unchanged.

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

apps/api/src/services/job-manager.ts

@@ -4,7 +4,7 @@
 
 import type * as k8s from '@kubernetes/client-node';
 
-const WORKER_LABEL = 'shannon-worker';
+const WORKER_LABEL = 'hightower-worker';
 
 export async function createJob(batchApi: k8s.BatchV1Api, namespace: string, job: k8s.V1Job): Promise<void> {
   await batchApi.createNamespacedJob({ namespace, body: job });