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/src/api/auth.ts

@@ -0,0 +1,35 @@
+/**
+ * Authentication API
+ */
+
+import axios from 'axios';
+import { API_BASE_URL } from '../config/api';
+import type { LoginCredentials, AuthResponse, User } from '../types';
+import apiClient from './client';
+
+// Login uses the main auth endpoint, not the mobile API
+const authAxios = axios.create({
+  baseURL: API_BASE_URL,
+  timeout: 30000,
+  headers: {
+    'Content-Type': 'application/json',
+  },
+});
+
+export async function loginApi(credentials: LoginCredentials): Promise<AuthResponse> {
+  const response = await authAxios.post<AuthResponse>('/auth/login/', credentials);
+  return response.data;
+}
+
+export async function getProfile(): Promise<User> {
+  const response = await apiClient.get<User>('/me/');
+  return response.data;
+}
+
+export async function logoutApi(): Promise<void> {
+  try {
+    await apiClient.post('/logout/');
+  } catch (error) {
+    // Ignore logout errors
+  }
+}