feat: add database config and migration system

server/db/migrate.js

@@ -0,0 +1,44 @@
+const fs = require('fs');
+const path = require('path');
+const db = require('../config/database');
+
+const migrationsDir = path.join(__dirname, 'migrations');
+
+function getExecutedMigrations() {
+  try {
+    return db.prepare('SELECT name FROM migrations').all().map(m => m.name);
+  } catch (err) {
+    // migrations 表可能还不存在（第一次运行）
+    return [];
+  }
+}
+
+function runMigration(filename) {
+  const filepath = path.join(migrationsDir, filename);
+  const sql = fs.readFileSync(filepath, 'utf-8');
+
+  console.log(`Running migration: ${filename}`);
+  db.exec(sql);
+  db.prepare('INSERT INTO migrations (name) VALUES (?)').run(filename);
+  console.log(`Completed: ${filename}`);
+}
+
+function migrate() {
+  const executed = getExecutedMigrations();
+  const files = fs.readdirSync(migrationsDir)
+    .filter(f => f.endsWith('.sql'))
+    .filter(f => !executed.includes(f))
+    .sort();
+
+  for (const file of files) {
+    runMigration(file);
+  }
+
+  if (files.length === 0) {
+    console.log('No pending migrations.');
+  } else {
+    console.log(`Completed ${files.length} migration(s).`);
+  }
+}
+
+migrate();