docs: add work log for 2026-06-15 and update DB deletion policy in README

scratch/raw_check.cjs

@@ -0,0 +1,18 @@
+const mysql = require('mysql2/promise');
+require('dotenv').config();
+
+async function rawCheck() {
+  const connection = await mysql.createConnection({
+    host: process.env.DB_HOST,
+    user: process.env.DB_USER,
+    password: process.env.DB_PASS,
+    database: process.env.DB_NAME,
+    port: parseInt(process.env.DB_PORT || '3306')
+  });
+
+  const [rows] = await connection.query('SELECT user_current, emp_no FROM asset_core WHERE id LIKE "PC_20260615_%" LIMIT 10');
+  console.log(rows);
+  await connection.end();
+}
+
+rawCheck().catch(console.error);