fix(transport): NavMenu Admin-only visibility + BundleImportUnlockFailed audit + docker appsettings

- NavMenu: move Import Bundle out of the nested RequireDesign/RequireAdmin
  double-gate into the top-level Admin section so an Admin-only user sees it
  without needing the Design role; Export Bundle stays in the Design section.
- TransportImport: inject IAuditService + ScadaLinkDbContext; emit a
  BundleImportUnlockFailed audit row (best-effort, swallowed on failure) on
  every wrong-passphrase attempt in SubmitPassphraseAsync, with attempt
  number and error reason in afterState.
- docker central-node-a/b appsettings: add ScadaLink:Transport section with
  SourceEnvironment = "docker-cluster" so the importer picks up a non-null
  environment name in the audit trail.
- CentralUI.Tests: register IAuditService mock + SQLite in-memory
  ScadaLinkDbContext in TransportImportPageTests to satisfy the two new injects.

docker/central-node-a/appsettings.Central.json

@@ -58,6 +58,9 @@
       "DispatchInterval": "00:00:05",
       "DispatchBatchSize": 1000
     },
+    "Transport": {
+      "SourceEnvironment": "docker-cluster"
+    },
     "Logging": {
       "MinimumLevel": "Information"
     }