feat: 添加 hydrogen_energy 数据库连接和里程管理类型定义

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

src/server/mileage-db.ts

@@ -0,0 +1,14 @@
+import mysql from 'mysql2/promise';
+
+const mileagePool = mysql.createPool({
+  host: '101.133.130.65',
+  port: 3306,
+  user: 'bi_reader_02',
+  password: 'bi_reader_02_Pass',
+  database: 'hydrogen_energy',
+  waitForConnections: true,
+  connectionLimit: 5,
+  queueLimit: 0,
+});
+
+export default mileagePool;