chore(auth): ScadaBridge unify dev LDAP base DN to dc=zb,dc=local (Task 1.6)

Replace dc=scadabridge,dc=local with dc=zb,dc=local in all dev/test LDAP
references — app config, docker test-cluster node configs (docker/ and
docker-env2/), GLAuth fixture, dev tooling, Host.Tests fixtures,
IntegrationTests factory, and operational test_infra docs. OU structure
(ou=SCADA-Admins,ou=users,etc.) preserved throughout. Email domains
(@scadabridge.local), hostnames, and container names are untouched.
Historical plan docs (2026-05-24-second-environment.md,
2026-05-31-folder-repo-rename-scadabridge-design.md) excluded as
point-in-time records. No synthetic dc=example,dc=com placeholders touched.

docs/test_infra/test_infra.md

@@ -67,7 +67,7 @@ For use in `appsettings.Development.json`:
   "Ldap": {
     "Server": "localhost",
     "Port": 3893,
-    "BaseDN": "dc=scadabridge,dc=local",
+    "BaseDN": "dc=zb,dc=local",
     "UseSsl": false
   },
   "OpcUa": {