feat: add MariaDB schema and connection pool

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

db/schema.sql

@@ -0,0 +1,19 @@
+CREATE TABLE IF NOT EXISTS conversion_jobs (
+  id CHAR(36) NOT NULL PRIMARY KEY,
+  status ENUM('pending', 'processing', 'done', 'failed') NOT NULL DEFAULT 'pending',
+  family VARCHAR(32) NOT NULL,
+  source_format VARCHAR(16) NOT NULL,
+  target_format VARCHAR(16) NOT NULL,
+  original_filename VARCHAR(255) NOT NULL,
+  input_path VARCHAR(255) NOT NULL,
+  output_path VARCHAR(255) NULL,
+  input_mime_type VARCHAR(128) NOT NULL,
+  output_mime_type VARCHAR(128) NULL,
+  error_message VARCHAR(255) NULL,
+  error_log TEXT NULL,
+  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  expires_at DATETIME NOT NULL,
+  INDEX idx_status (status),
+  INDEX idx_expires_at (expires_at)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

src/db.js

@@ -0,0 +1,23 @@
+import mariadb from 'mariadb';
+
+let pool;
+
+export function getPool(config) {
+  if (!pool) {
+    pool = mariadb.createPool({
+      host: config.db.host,
+      user: config.db.user,
+      password: config.db.password,
+      database: config.db.database,
+      connectionLimit: 10,
+    });
+  }
+  return pool;
+}
+
+export async function closePool() {
+  if (pool) {
+    await pool.end();
+    pool = undefined;
+  }
+}

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);
+  });
+});