feat(topbar): unread/queue badges + Approvals tab

App.tsx polls every 60s when authed + tenant known:
- chatApi.listThreads + listMessages -> count threads with last message
  from someone else after our localStorage read mark
- api.workItems filtered by tenant -> queue count

Badge UI:
- Chat tab shows amber unread pill (99+ cap)
- Approvals tab (new in topbar) shows navy queue-count pill

Also promotes Approvals to a first-class topbar tab (was landing-chip
only). 60s poll is identical to existing live-tick cadence so this
adds no extra polling load.

src/index.css

@@ -2225,3 +2225,15 @@ select.studio-input { background: var(--bp-paper); }
   .wizard-body { padding: 0 12px 12px; }
   .wizard-preview { position: static; max-height: none; }
 }
+
+.tab-badge {
+  display: inline-flex; align-items: center; justify-content: center;
+  margin-left: 4px;
+  min-width: 18px; padding: 0 5px; height: 16px;
+  background: var(--bp-navy); color: var(--bp-paper);
+  font-family: var(--bp-mono); font-size: 9px; font-weight: 700; line-height: 1;
+}
+.tab-badge-amber { background: var(--bp-amber); color: var(--bp-paper); }
+@media (max-width: 700px) {
+  .tab-badge { min-width: 14px; height: 12px; font-size: 8px; padding: 0 3px; }
+}