fix: restore post-v1.1.14 features while preserving asset updates

Undo the full-tree rollback in 6ea1b3d and restore the pre-rollback v1.2.0 code. Preserve the new asset flow rules, abnormal inventory separation, range drilldowns and date picker; adapt the regression test to the restored routes layout.

src/server/db/mysql.ts

@@ -0,0 +1,17 @@
+import mysql from 'mysql2/promise';
+import dotenv from 'dotenv';
+
+dotenv.config();
+
+const pool = mysql.createPool({
+  host: process.env.DB_HOST,
+  port: Number(process.env.DB_PORT) || 3306,
+  user: process.env.DB_USER,
+  password: process.env.DB_PASSWORD,
+  database: process.env.DB_NAME,
+  waitForConnections: true,
+  connectionLimit: 10,
+  queueLimit: 0,
+});
+
+export default pool;