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/Dockerfile

@@ -0,0 +1,19 @@
+FROM node:18-alpine
+
+WORKDIR /app
+
+# Install dependencies
+COPY package*.json ./
+RUN npm install
+
+# Copy source code
+COPY . .
+
+# Expose port
+EXPOSE 3000
+
+# Set environment variable for API URL
+ENV REACT_APP_API_URL=http://localhost:3001/api
+
+# Start development server
+CMD ["npm", "start"]