Add click-to-lock row highlighting

Clicking a row locks an orange highlight (#fff7e6) across the whole row
including fixed columns; clicking the same row unlocks, clicking another
switches. Lock resets on search/clear. Highlight survives horizontal scroll
since rowClassName applies to all row fragments.

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

src/app/globals.css

@@ -6,3 +6,8 @@ body {
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
     "Helvetica Neue", Arial, sans-serif;
 }
+
+/* 行高亮：点击锁定的整行（覆盖 antd 单元格背景，含固定列） */
+.ant-table-tbody > tr.row-locked > td {
+  background: #fff7e6 !important;
+}