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/.env.example

@@ -0,0 +1,10 @@
+# API Configuration
+# For development, use your local backend URL
+# For Android emulator, use 10.0.2.2 instead of localhost
+EXPO_PUBLIC_API_BASE_URL=http://10.0.2.2:8000
+
+# For iOS simulator, use localhost
+# EXPO_PUBLIC_API_BASE_URL=http://localhost:8000
+
+# For production
+# EXPO_PUBLIC_API_BASE_URL=https://api.smoothschedule.com