Add PostgreSQL schema and migration runner

All tables per PRD data model with default config seeds.
Migration runner tracks applied migrations in DB.

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

server/src/db.js

@@ -1,7 +1,12 @@
 const { Pool } = require('pg');
+const { runMigrations } = require('../../db/migrations/001_initial_schema');
 
 const pool = new Pool({
   connectionString: process.env.DATABASE_URL,
 });
 
-module.exports = pool;
+async function initialize() {
+  await runMigrations(pool);
+}
+
+module.exports = { pool, runMigrations, initialize };

server/src/index.js

@@ -3,6 +3,7 @@ const express = require('express');
 const cors = require('cors');
 const path = require('path');
 const healthRouter = require('./routes/health');
+const db = require('./db');
 
 const app = express();
 const PORT = process.env.PORT || 3000;
@@ -22,6 +23,9 @@ app.get('*', (req, res) => {
   res.sendFile(path.join(clientDist, 'index.html'));
 });
 
-app.listen(PORT, () => {
-  console.log(`Server running on port ${PORT}`);
-});
+(async () => {
+  await db.initialize();
+  app.listen(PORT, () => {
+    console.log(`Server running on port ${PORT}`);
+  });
+})();