feat(messenger): CRM consumes @insignia/iios-messaging-ui instead of embedding

The messenger tab now renders the shared SDK's <Messenger>, not the bespoke
in-CRM implementation. The CRM only supplies transport + theme:

- CrmMessagingAdapter implements the SDK's MessagingAdapter over the be-crm
  data door (crm.messenger.conversation.list/open, history, send, directory);
  live updates via a 4s poll for now (socket realtime is a follow-up that
  reuses messenger-socket.tsx). Tenancy/auth stay server-side.
- messenger-sdk.tsx wires MessagingProvider + adapter (live = CrmMessagingAdapter,
  demo = the SDK MockAdapter), themed by mapping --miu-* tokens to the CRM
  design system.
- dashboard renders <MessengerSdk/>; the old messenger.tsx is left in place
  for rollback and will be deleted once this is proven live.

NOTE: the SDK is installed from a local tarball (file:) for verification since
it isn't published yet. For deploy: publish @insignia/iios-messaging-ui to the
registry and change the dep to a version range. transpilePackages covers ESM.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

next.config.ts

@@ -1,8 +1,8 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  // The SDK ships ESM/TS; let Next transpile it.
-  transpilePackages: ["@abe-kap/appshell-sdk"],
+  // The SDKs ship ESM; let Next transpile them.
+  transpilePackages: ["@abe-kap/appshell-sdk", "@insignia/iios-messaging-ui"],
   // The browser calls the Shell BFF same-origin under /shell (so the HttpOnly
   // session cookie flows). We deliberately use /shell (NOT /api) to avoid
   // clobbering the existing /api/geo route. Point BFF_ORIGIN at the deployed BFF.