Initial commit: MVP scaffolding for Line of Sight application

- React frontend with MapLibre integration
- Node.js Express backend with dummy API
- Docker containerization (PostgreSQL+PostGIS, backend, frontend)
- Interactive map with direction selector
- 20 mock conurbations data
- Full project structure ready for PR workflow

frontend/src/services/api.js

@@ -0,0 +1,25 @@
+import axios from 'axios';
+
+const API_BASE_URL = process.env.REACT_APP_API_URL || 'http://localhost:3001/api';
+
+const api = axios.create({
+  baseURL: API_BASE_URL,
+  timeout: 10000,
+  headers: {
+    'Content-Type': 'application/json'
+  }
+});
+
+export const getLineOfSight = async (lat, lon, direction, tolerance) => {
+  const response = await api.get('/line-of-sight', {
+    params: { lat, lon, direction, tolerance }
+  });
+  return response;
+};
+
+export const healthCheck = async () => {
+  const response = await api.get('/health');
+  return response;
+};
+
+export default { getLineOfSight, healthCheck };