Add Docker Compose project scaffold

Sets up the full monorepo structure with:
- Multi-stage Dockerfile (client-build + production stages)
- docker-compose.yml for production, docker-compose.dev.yml overlay for development
- Express server (port 3000) with pg pool, health route, and SPA static file serving
- React 18 + Vite client with react-router-dom v6, nav bar, and placeholder page components
- .env.example with PostgreSQL and app config
- Empty db/migrations/ directory for future migrations
- CLAUDE.md updated with development workflow commands

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "budget-server",
+  "version": "1.0.0",
+  "main": "src/index.js",
+  "scripts": {
+    "start": "node src/index.js",
+    "dev": "nodemon src/index.js"
+  },
+  "dependencies": {
+    "cors": "^2.8.5",
+    "dotenv": "^16.4.5",
+    "express": "^4.19.2",
+    "pg": "^8.11.5"
+  },
+  "devDependencies": {
+    "nodemon": "^3.1.0"
+  }
+}

server/src/db.js

@@ -0,0 +1,7 @@
+const { Pool } = require('pg');
+
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL,
+});
+
+module.exports = pool;

server/src/index.js

@@ -0,0 +1,27 @@
+require('dotenv').config();
+const express = require('express');
+const cors = require('cors');
+const path = require('path');
+const healthRouter = require('./routes/health');
+
+const app = express();
+const PORT = process.env.PORT || 3000;
+
+app.use(cors());
+app.use(express.json());
+
+// API routes
+app.use('/api', healthRouter);
+
+// Serve static client files in production
+const clientDist = path.join(__dirname, '../../client/dist');
+app.use(express.static(clientDist));
+
+// SPA fallback — send index.html for any unmatched route
+app.get('*', (req, res) => {
+  res.sendFile(path.join(clientDist, 'index.html'));
+});
+
+app.listen(PORT, () => {
+  console.log(`Server running on port ${PORT}`);
+});

server/src/routes/health.js

@@ -0,0 +1,8 @@
+const express = require('express');
+const router = express.Router();
+
+router.get('/health', (req, res) => {
+  res.status(200).json({ status: 'ok' });
+});
+
+module.exports = router;