Bypass connection overlay in captive portal mode

Apple's captive portal webview (captive.apple.com) blocks WebSocket
connections, causing the app to get stuck on "Connecting to Backend".

Detect captive portal context by checking window.location.hostname
against known OS probe domains. When detected:
- Skip the WebSocket connection blocking overlay
- Auto-redirect to /wifi-setup page

HTTP API calls still work fine through DNS redirect, so the WiFi
setup page functions normally in the captive portal webview.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/layout/Layout.tsx

@@ -24,6 +24,21 @@ const navItems = [
 
 const DEFAULT_APP_NAME = 'Dune Weaver'
 
+// Detect captive portal context (DNS-redirected domains used by OS probe requests)
+const CAPTIVE_PORTAL_HOSTS = [
+  'captive.apple.com',
+  'connectivitycheck.gstatic.com',
+  'connectivitycheck.android.com',
+  'clients3.google.com',
+  'nmcheck.gnome.org',
+  'network-test.debian.org',
+  'msftconnecttest.com',
+  'www.msftconnecttest.com',
+]
+const isCaptivePortal = CAPTIVE_PORTAL_HOSTS.some(
+  (h) => window.location.hostname === h || window.location.hostname.endsWith('.' + h)
+)
+
 export function Layout() {
   const location = useLocation()
   const navigate = useNavigate()
@@ -33,6 +48,13 @@ export function Layout() {
     window.scrollTo(0, 0)
   }, [location.pathname])
 
+  // Captive portal: redirect straight to WiFi setup
+  useEffect(() => {
+    if (isCaptivePortal && location.pathname !== '/wifi-setup') {
+      navigate('/wifi-setup', { replace: true })
+    }
+  }, [location.pathname, navigate])
+
   // Multi-table context - must be called before any hooks that depend on activeTable
   const { activeTable, tables } = useTable()
 
@@ -1293,8 +1315,9 @@ export function Layout() {
       )}
 
       {/* Backend Connection / Homing Blocking Overlay */}
+      {/* Skip in captive portal mode (WebSocket won't connect in sandboxed webview) */}
       {/* Don't show this overlay when sensor homing failed - that has its own dialog */}
-      {!sensorHomingFailed && (!isBackendConnected || (isHoming && !homingDismissed) || homingJustCompleted) && (
+      {!isCaptivePortal && !sensorHomingFailed && (!isBackendConnected || (isHoming && !homingDismissed) || homingJustCompleted) && (
         <div className="fixed inset-0 z-50 bg-background/95 backdrop-blur-sm flex flex-col items-center justify-center p-4">
           <div className="w-full max-w-2xl space-y-6">
             {/* Status Header */}