docs: former-api-specs (MES + DNC/Delmia) + inbound compile-error known issue

- former-api-specs/mes: Alarm-API, MoveIn-MoveOut-API, API-key authgaps (from ~/Desktop/mesapi)
- former-api-specs/dnc: Delmia-Integration-API — Delmia document service + WW recipe-download notify (from ~/Desktop/delmiaintegration)
- known-issues: inbound API compile error not client-visible; no api-method validate

docs/former-api-specs/README.md

@@ -0,0 +1,18 @@
+# Former API Specs
+
+Reference specifications for the **predecessor / legacy APIs** that ScadaBridge replaces or
+interoperates with. These are *not* ScadaBridge's own contracts — they are kept here as
+historical reference when porting integrations onto ScadaBridge's Inbound API (#14) and
+External System Gateway (#7), and for parity-checking behavior during cutover.
+
+ScadaBridge's own component design docs live under [`docs/requirements/`](../requirements);
+this folder holds only the **outgoing/legacy** systems' specs.
+
+## Subfolders
+
+- [`mes/`](mes) — the legacy MES API (ServiceStack "WWSupport / APIServer", a.k.a. `mesapi`)
+  that bridges MES ↔ AVEVA Wonderware via MXAccess. Source repo: `~/Desktop/mesapi`.
+- [`dnc/`](dnc) — the legacy DNC integration: DELMIA Apriso document/recipe download +
+  Wonderware recipe-download notification (`~/Desktop/delmiaintegration`).
+
+Drop the relevant spec documents into the matching subfolder.