Initial commit: Price Hunter — self-hosted price comparison engine

Complete application scaffolding with:
- Backend: Node.js + Fastify + sql.js (SQLite)
- Frontend: SvelteKit + Tailwind CSS
- Scraper engine with parallel fan-out, rate limiting, cheerio-based parsing
- Store management with CSS selector config and per-store test pages
- Docker setup for single-command deployment

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/db/migrate.ts

@@ -0,0 +1,51 @@
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { getDatabase, saveDatabase } from './connection.js';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
+export function runMigrations(): void {
+  const db = getDatabase();
+
+  db.run(`
+    CREATE TABLE IF NOT EXISTS _migrations (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      name TEXT NOT NULL UNIQUE,
+      applied_at TEXT DEFAULT (datetime('now'))
+    )
+  `);
+
+  const migrationsDir = path.join(__dirname, 'migrations');
+
+  // In production (compiled), migrations may be alongside the compiled JS
+  const altMigrationsDir = path.join(__dirname, '..', '..', '..', 'src', 'server', 'db', 'migrations');
+  const dir = fs.existsSync(migrationsDir) ? migrationsDir : (fs.existsSync(altMigrationsDir) ? altMigrationsDir : null);
+
+  if (!dir) {
+    console.warn('No migrations directory found');
+    return;
+  }
+
+  const files = fs.readdirSync(dir)
+    .filter((f) => f.endsWith('.sql'))
+    .sort();
+
+  const appliedStmt = db.prepare('SELECT name FROM _migrations');
+  const applied = new Set<string>();
+  while (appliedStmt.step()) {
+    applied.add(appliedStmt.getAsObject().name as string);
+  }
+  appliedStmt.free();
+
+  for (const file of files) {
+    if (applied.has(file)) continue;
+
+    const sql = fs.readFileSync(path.join(dir, file), 'utf-8');
+    db.run(sql);
+    db.run('INSERT INTO _migrations (name) VALUES (?)', [file]);
+    console.log(`Migration applied: ${file}`);
+  }
+
+  saveDatabase();
+}