fix(harbor): correct naming convention and use staging certs

- Rename application/namespace: the-seas -> harbor
- Move directory: cluster/platform/the-seas -> cluster/platform/harbor
- Update all resource references (ExternalSecret, HTTPRoutes, Certificates)
- Switch to letsencrypt-staging issuer (avoid ACME rate limits during testing)
- Thematic name 'the-seas' remains in DNS hostnames and comments

cluster/platform/harbor/certificate.yaml

@@ -0,0 +1,16 @@
+# ------------------------------------------------------------------------------
+# Certificate — Harbor TLS Certificate (staging until stable)
+# Primary DNS: the-seas.local.mk-labs.cloud
+# ------------------------------------------------------------------------------
+apiVersion: cert-manager.io/v1
+kind: Certificate
+metadata:
+  name: harbor-tls
+  namespace: harbor
+spec:
+  secretName: harbor-tls
+  issuerRef:
+    name: letsencrypt-staging
+    kind: ClusterIssuer
+  dnsNames:
+    - the-seas.local.mk-labs.cloud