feat: 맞춤 집계표 엑셀 다운로드 추가

- 조회 폼에 '엑셀저장' 버튼(현재 컬럼·필터·제목·집계방식 그대로 반영)
- Excel 2003 XML로 제목·기간·품목구분 머리행 + 선택 컬럼 + 합계행 출력

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Controllers/Admin/SalesReport.php

@@ -3556,6 +3556,38 @@ class SalesReport extends BaseController
             }
         }
 
+        // 엑셀 다운로드 — 현재 컬럼·필터·제목 그대로
+        if ((string) ($this->request->getGet('export') ?? '') === '1') {
+            $headers = array_map(static fn ($k) => self::CUSTOM_REPORT_COLUMNS[$k]['label'], $selected);
+            $exportRows = [];
+            foreach ($rows as $row) {
+                $line = [];
+                foreach ($selected as $key) {
+                    $isNum  = (self::CUSTOM_REPORT_COLUMNS[$key]['type'] ?? '') === 'num';
+                    $line[] = $isNum ? number_format((int) ($row[$key] ?? 0)) : (string) ($row[$key] ?? '');
+                }
+                $exportRows[] = $line;
+            }
+            // 합계 행
+            $totalLine = [];
+            foreach ($selected as $i => $key) {
+                $isNum = (self::CUSTOM_REPORT_COLUMNS[$key]['type'] ?? '') === 'num';
+                if ($i === 0) {
+                    $totalLine[] = '합계';
+                } else {
+                    $totalLine[] = $isNum ? number_format((int) ($totals[$key] ?? 0)) : '';
+                }
+            }
+            $exportRows[] = $totalLine;
+
+            $fileTitle = $title !== '' ? $title : '맞춤집계표';
+            $topRows   = [
+                [$fileTitle],
+                ['조회기간: ' . $startDate . ' ~ ' . $endDate . ' / 품목구분: ' . $this->customReportCategoryLabel($category)],
+            ];
+            export_excel_2003_xml($fileTitle . '_' . $startDate . '_' . $endDate, mb_substr($fileTitle, 0, 31), $headers, $exportRows, $topRows);
+        }
+
         return $this->renderWorkPage('맞춤 집계표', 'admin/sales_report/custom_report', [
             'columnCatalog'  => self::CUSTOM_REPORT_COLUMNS,
             'selected'       => $selected,