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>

src/components/dashboard/dashboard.tsx

@@ -15,7 +15,7 @@ import { Support } from "./support";
 import { Rules } from "./rules";
 import { AiAssistant } from "./ai-assistant";
 import { TeamManagement } from "./team-management";
-import { Messenger } from "./messenger";
+import { MessengerSdk } from "./messenger-sdk";
 import { Inbox } from "./inbox";
 import "../../app/dashboard/dashboard.css";
 
@@ -47,7 +47,7 @@ export function Dashboard() {
               : active === "support" ? <Support />
               : active === "rules" ? <Rules />
               : active === "ai" ? <AiAssistant />
-              : active === "messenger" ? <Messenger />
+              : active === "messenger" ? <MessengerSdk />
               : active === "inbox" ? <Inbox />
               : active === "team" ? <TeamManagement />
               : <ComingSoon title={title} icon={item?.icon ?? "dashboard"} onGo={setActive} />}