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

docker-compose.yml

@@ -0,0 +1,55 @@
+version: '3.8'
+
+services:
+  postgres:
+    image: postgis/postgis:15-3.3-alpine
+    container_name: line-of-sight-db
+    environment:
+      POSTGRES_DB: line_of_sight
+      POSTGRES_USER: line_of_sight
+      POSTGRES_PASSWORD: line_of_sight_pass
+    ports:
+      - "5432:5432"
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+      - ./docker/init.sql:/docker-entrypoint-initdb.d/init.sql
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U line_of_sight"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+  backend:
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    container_name: line-of-sight-backend
+    ports:
+      - "3001:3001"
+    environment:
+      - DATABASE_URL=postgresql://line_of_sight:line_of_sight_pass@postgres:5432/line_of_sight
+      - PORT=3001
+    depends_on:
+      postgres:
+        condition: service_healthy
+    volumes:
+      - ./backend:/app
+      - /app/node_modules
+
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile
+    container_name: line-of-sight-frontend
+    ports:
+      - "3000:3000"
+    environment:
+      - REACT_APP_API_URL=http://localhost:3001/api
+    depends_on:
+      - backend
+    volumes:
+      - ./frontend:/app
+      - /app/node_modules
+
+volumes:
+  pgdata: