feat: add MariaDB schema and connection pool

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

test/db.test.js

@@ -0,0 +1,26 @@
+import { describe, it, expect, afterAll } from 'vitest';
+import { getPool, closePool } from '../src/db.js';
+import { loadConfig } from '../src/config.js';
+
+describe('getPool', () => {
+  afterAll(async () => {
+    await closePool();
+  });
+
+  it('returns a working pool that can run a query', async () => {
+    const config = loadConfig();
+    const pool = getPool(config);
+
+    const rows = await pool.query('SELECT 1 AS value');
+
+    expect(Number(rows[0].value)).toBe(1);
+  });
+
+  it('returns the same pool instance on repeated calls', () => {
+    const config = loadConfig();
+    const poolA = getPool(config);
+    const poolB = getPool(config);
+
+    expect(poolA).toBe(poolB);
+  });
+});