Merge release/delivery (IAM single sign-on) into the triage work

Brings the four release/delivery commits (IAM SSO for the admin panel,
both apps and the API; IAM env in docker-compose) onto fix/issues-triage.

Conflicts:
- customer-auth.service.ts imports: both kept.
- both apps' api/client.ts: both kept (AccountingBalance/WageQuote, and
  iamAppUrl).
- all build output (admin-panel, user-app, user-app-v2 dist, and the api
  release bundle): rebuilt from the merged source instead of picking a
  side.

Fixed while verifying:
- The IAM change calls iam.browserBootstrapUrl after every login, but
  the identity-service stand-ins in three test files lacked it. 15 tests
  failed on release/delivery itself.
- SMS relay: SMS_RELAY_PLATFORM was read but never sent, so the gateway
  never got `platform` (documented body: phone, host, text, platform).
  relayConfig() now returns it ("default" → null) and the request carries
  it. sms.service.spec now passes.

All 249 API tests pass; the three front-ends type-check and build.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/user-app/src/views/user/DashboardView.vue

@@ -237,9 +237,20 @@ function goToDetails(id: number) {
   if (id === 6) router.push({ name: 'report' })
 }
 
-function logOut() {
-  session.logout()
+async function logOut() {
   data.notify = false
+  let central: string | null = null
+  try {
+    central = (await api.ssoLogoutUrl()).logout_url
+  } catch {
+    central = null
+  }
+  session.logout()
+  sessionStorage.removeItem('gb_iam_sso_checked')
+  if (central) {
+    window.location.assign(central)
+    return
+  }
   router.push({ name: 'home' })
 }