Add Excel export feature for full production data

Add "导出全部" button that exports all contract production data to an
.xlsx file via a new API endpoint using exceljs, with formatted headers,
date columns, auto-width, and frozen header row.

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

package.json

@@ -14,6 +14,7 @@
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",
     "antd": "^6.4.3",
+    "exceljs": "^4.4.0",
     "mssql": "^12.5.5",
     "next": "16.2.9",
     "react": "19.2.4",