feat(dashboard): live notifications phase 1 — presence, live unread, in-app toasts

Shared RealtimeProvider opens ONE dashboard-wide IIOS message socket reused by
the messenger tab and the new NotificationCenter. CrmMessagingAdapter gains
setFocus (drives presence/push suppression) and subscribeActivity (joins all
of the caller's threads, fans out incoming messages). NotificationCenter shows
a clickable toast on new messages when you're not on the messenger tab and
deep-links to the conversation. Pulls @insignia/iios-messaging-ui@0.1.7.

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

src/app/dashboard/dashboard.css

@@ -1272,3 +1272,6 @@
   .dash-root .gs-snippet em { color: var(--orange); font-style: normal; font-weight: 600; }
   .dash-root .gs-surface { flex: 0 0 auto; font-size: 10.5px; font-weight: 700; letter-spacing: 0.04em; text-transform: uppercase; color: var(--faint); }
   @media (max-width: 720px) { .dash-root .gs-field { width: 160px; } }
+
+  .dash-root .ds-toast.is-clickable .ds-toast-body { cursor: pointer; }
+  .dash-root .ds-toast.is-clickable .ds-toast-body:hover .ds-toast-title { color: var(--orange); }