refactor: scrub residual ScadaLink refs → ScadaBridge (env vars, config keys, assembly name, SQL login)

Renames the 13 SCADALINK_* runtime env vars → SCADABRIDGE_*, the ScadaLink__
.NET config keys → ScadaBridge__, the stale ScadaLink.Host.exe assembly name
→ ZB.MOM.WW.ScadaBridge.Host.exe, the scadalink_app SQL login → scadabridge_app,
and residual identifiers/comments/docs. Migration records (prior rename
tooling/design, DB-rename helper, this scrub script) carved out.

Adds tools/scrub-scadalink-refs.sh.

docs/plans/2026-05-24-transport-design.md

@@ -81,7 +81,7 @@ Exactly one of `content.json` or `content.enc` is present.
   "createdAtUtc": "2026-05-24T12:34:56Z",
   "sourceEnvironment": "dev-cluster-a",
   "exportedBy": "alice@corp.example",
-  "scadaLinkVersion": "1.4.2",
+  "scadaBridgeVersion": "1.4.2",
   "contentHash": "sha256:...",
   "encryption": {
     "algorithm": "AES-256-GCM",