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/app/dashboard/dashboard.css

@@ -133,6 +133,20 @@
   
   .dash-content { padding: 22px 28px 40px; width: 100%; }
   .sec-title { font-size: 15px; font-weight: 700; margin: 6px 0 14px; }
+
+  /* Host for @insignia/iios-messaging-ui: a fixed-height card that maps the SDK's --miu-* tokens
+     onto the CRM design system, so the drop-in SDK matches the rest of the app. */
+  .dash-root .miu-host { height: 620px; border: 1px solid var(--border); border-radius: 16px; overflow: hidden; }
+  .dash-root .miu-host .miu-messenger {
+    --miu-bg: var(--bg);
+    --miu-panel: var(--panel);
+    --miu-panel-2: var(--panel-2);
+    --miu-border: var(--border);
+    --miu-text: var(--text);
+    --miu-muted: var(--muted);
+    --miu-accent: var(--orange);
+    --miu-accent-text: #1a1206;
+  }
   
   /* ---- grid helpers ---- */
   .grid { display: grid; gap: 16px; }