feat(mobile): Add field app with date range navigation

- Add React Native Expo field app for mobile staff
- Use main /appointments/ endpoint with date range support
- Add X-Business-Subdomain header for tenant context
- Support day/week view navigation
- Remove WebSocket console logging from frontend
- Update AppointmentStatus type to include all backend statuses
- Add responsive status legend to scheduler header

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mobile/field-app/app/index.tsx

@@ -0,0 +1,20 @@
+/**
+ * Index - Redirects to the appropriate screen
+ */
+
+import { Redirect } from 'expo-router';
+import { useAuth } from '../src/hooks/useAuth';
+
+export default function Index() {
+  const { isAuthenticated, isLoading } = useAuth();
+
+  if (isLoading) {
+    return null;
+  }
+
+  if (isAuthenticated) {
+    return <Redirect href="/(auth)/jobs" />;
+  }
+
+  return <Redirect href="/login" />;
+}