fix: 报表导出增加诊断日志

在 CSV/XLSX 导出时记录 raw_rows 数量和 detail_map 周期键，
用于排查导出缺少订单明细的问题。

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

backend/app/services/export_service.py

@@ -128,6 +128,12 @@ class ExportService:
             raw_rows (list): 订单明细行列表，用于追加明细数据
         """
         detail_map = self._build_detail_map(raw_rows, report["stat_type"])
+        import logging
+        _log = logging.getLogger(__name__)
+        _log.info("[CSV导出] stat_type=%s, 汇总周期数=%d, raw_rows=%d, detail_map周期=%s",
+                  report["stat_type"], len(report["list"]),
+                  len(raw_rows) if raw_rows else 0,
+                  list(detail_map.keys()) if detail_map else "空")
         with file_path.open("w", encoding="utf-8-sig", newline="") as csvfile:
             writer = csv.writer(csvfile)
             writer.writerow(["统计周期", "订单数", "订单金额", "固定提成", "分类明细"])
@@ -147,6 +153,7 @@ class ExportService:
                         (detail.created_at.strftime("%Y-%m-%d") if detail.created_at else ""),
                     ])
             writer.writerow(self._build_summary_row(report["list"]))
+        _log.info("[CSV导出] 写入完成，文件=%s, 行数=%d", file_path.name, sum(1 for _ in file_path.open(encoding="utf-8-sig")))
 
     def _write_xlsx(self, file_path: Path, report: dict, raw_rows: list | None = None) -> None:
         """将报表汇总和订单明细写入 Excel 文件。
@@ -180,7 +187,10 @@ class ExportService:
         sheet.column_dimensions["E"].width = 48
 
         # Sheet 2: 订单明细
+        import logging
+        _log_xlsx = logging.getLogger(__name__)
         if raw_rows:
+            _log_xlsx.info("[XLSX导出] 订单明细行数=%d", len(raw_rows))
             detail_sheet = workbook.create_sheet("订单明细")
             detail_sheet.append(["统计周期", "订单号", "客户", "产品", "数量", "单价", "金额", "利润", "提成", "日期"])
             for row in raw_rows: