GKE: register the remaining tools, add the registry CA issuer

Adds nine Applications — external-secrets, harbor, jenkins, postgresql,
redis, victoria-metrics-single, vmagent, node-exporter, grafana — bringing
the cluster to the homelab's full set. Every nameOverride is pinned, which
is load-bearing rather than cosmetic in at least three cases:
external-secrets (its service account name is what vault-backend's
serviceAccountRef and Vault's auth role bind to), victoria-metrics-single
(its Service renders as <release>-server, the address vmagent and Grafana
both hardcode) and harbor (the pipeline refers to its object names).

extra-manifests gains the ClusterIssuer that makes cert-manager useful
here: a CA issuer over the registry-ca Secret, which is created by hand
from terraform output because the CA's private key exists only in
Terraform state and nothing can reconcile it from git.

Two homelab-only things removed rather than left to confuse: the Tailscale
Harbor Ingress, and the homelab cluster's own entry point and values file,
which have no meaning in a GCP-only repo. app-of-secretstores and
app-of-extra-manifests now point at this cluster's Gitea over cluster DNS,
and harbor-robot-dockerconfig is keyed to this cluster's registry hostname
— docker matches stored credentials by exact host, so the homelab's would
have silently pushed unauthenticated.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LEsTefWWifp4ikvhHF5s6N

app-of-secretstores.yaml

@@ -18,7 +18,7 @@ metadata:
 spec:
   project: default
   source:
-    repoURL: 'http://gitea.192.168.1.7.nip.io/mukul/devops-infra-argo-config.git'
+    repoURL: 'http://gitea-http.gitea.svc.cluster.local:3000/gitadmin/devops-infra-argo-config-gcp.git'
     targetRevision: main
     path: secretstores
     directory: