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/(auth)/_layout.tsx

@@ -0,0 +1,41 @@
+/**
+ * Auth Group Layout
+ *
+ * Layout for authenticated screens with header navigation.
+ */
+
+import { Stack } from 'expo-router';
+import { useSafeAreaInsets } from 'react-native-safe-area-context';
+
+export default function AuthLayout() {
+  const insets = useSafeAreaInsets();
+
+  return (
+    <Stack
+      screenOptions={{
+        headerStyle: {
+          backgroundColor: '#2563eb',
+        },
+        headerTintColor: '#fff',
+        headerTitleStyle: {
+          fontWeight: 'bold',
+        },
+        // Ensure header accounts for status bar on Android
+        headerStatusBarHeight: insets.top,
+      }}
+    >
+      <Stack.Screen
+        name="jobs"
+        options={{
+          headerShown: false,
+        }}
+      />
+      <Stack.Screen
+        name="job/[id]"
+        options={{
+          title: 'Job Details',
+        }}
+      />
+    </Stack>
+  );
+}