feat: implement cross-batch Alipay refund reconciliation

When a refund row in an uploaded Alipay bill has no matching expense
row in the same batch (because the original purchase was uploaded in a
prior batch), the refund is now reconciled against the stored record in
bills_cleaned rather than being silently discarded.

Changes:
- analyzer/cleaners/base.py: add unresolved_refunds list to BaseCleaner
- analyzer/cleaners/alipay.py: _aggregate_refunds stores full refund
  metadata (dict); _process_expenses tracks matched keys and populates
  self.unresolved_refunds for unmatched refunds
- analyzer/server.py: thread unresolved_refunds through do_clean,
  CleanResponse, and both /clean endpoints
- server/adapter/adapter.go: add UnresolvedRefund type and field to CleanResult
- server/adapter/http/cleaner.go: deserialize unresolved_refunds from
  Python response and populate CleanResult
- server/repository/repository.go: add ReconcileRefund to BillRepository interface
- server/repository/mongo/repository.go: implement ReconcileRefund —
  full refund soft-deletes the bill, partial refund reduces amount and
  appends remark with original amount and refund order number
- server/handler/upload.go: capture clean result and call ReconcileRefund
  for each unresolved refund after saving cleaned bills
- server/model/response.go: add ReconciledRefundCount to UploadData

Also: add CLAUDE.md (@AGENTS.md), update AGENTS.md, fix DailyTrendChart
missing-date gap by filling zero-expense dates in daily map.

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

server/handler/upload.go

@@ -223,7 +223,7 @@ func Upload(c *gin.Context) {
 		End:    req.End,
 		Format: req.Format,
 	}
-	_, cleanErr := service.RunCleanScript(processFilePath, outputPath, cleanOpts)
+	cleanResult, cleanErr := service.RunCleanScript(processFilePath, outputPath, cleanOpts)
 	if cleanErr != nil {
 		service.CleanupExtractedFiles(extractedFiles)
 		c.JSON(http.StatusInternalServerError, model.UploadResponse{
@@ -255,22 +255,37 @@ func Upload(c *gin.Context) {
 	}
 	service.CleanupExtractedFiles(extractedFiles)
 
+	repo := repository.GetRepository()
+
 	// 13. 如果是京东账单，软删除其他来源中包含"京东-订单编号"的记录
 	var jdRelatedDeleted int64
-	if billType == "jd" {
-		repo := repository.GetRepository()
-		if repo != nil {
-			deleted, err := repo.SoftDeleteJDRelatedBills()
-			if err != nil {
-				fmt.Printf("⚠️  软删除京东关联记录失败: %v\n", err)
-			} else if deleted > 0 {
-				jdRelatedDeleted = deleted
-				fmt.Printf("🗑️  已软删除 %d 条其他来源中的京东关联记录\n", deleted)
+	if billType == "jd" && repo != nil {
+		deleted, err := repo.SoftDeleteJDRelatedBills()
+		if err != nil {
+			fmt.Printf("⚠️  软删除京东关联记录失败: %v\n", err)
+		} else if deleted > 0 {
+			jdRelatedDeleted = deleted
+			fmt.Printf("🗑️  已软删除 %d 条其他来源中的京东关联记录\n", deleted)
+		}
+	}
+
+	// 14. 核销跨批次退款（本次清洗中未在同批次内匹配到对应支出的退款）
+	var reconciledCount int
+	if repo != nil && cleanResult != nil {
+		for _, ur := range cleanResult.UnresolvedRefunds {
+			matched, rErr := repo.ReconcileRefund(billType, ur.OrderNo, ur.MerchantOrderNo, ur.Amount, ur.Time, ur.Merchant, ur.Description, ur.RefundOrderNo)
+			if rErr != nil {
+				fmt.Printf("⚠️  退款核销失败: %v\n", rErr)
+				continue
+			}
+			if matched {
+				reconciledCount++
+				fmt.Printf("💰 已核销退款: 订单%s, 金额%.2f元\n", ur.OrderNo, ur.Amount)
 			}
 		}
 	}
 
-	// 14. 返回成功响应
+	// 15. 返回成功响应
 	message := fmt.Sprintf("处理成功，新增 %d 条记录", cleanedCount)
 	if dedupResult.DuplicateCount > 0 {
 		message = fmt.Sprintf("处理成功，新增 %d 条，跳过 %d 条重复记录", cleanedCount, dedupResult.DuplicateCount)
@@ -278,18 +293,22 @@ func Upload(c *gin.Context) {
 	if jdRelatedDeleted > 0 {
 		message = fmt.Sprintf("%s，标记删除 %d 条重复的京东订单", message, jdRelatedDeleted)
 	}
+	if reconciledCount > 0 {
+		message = fmt.Sprintf("%s，核销退款 %d 条", message, reconciledCount)
+	}
 
 	c.JSON(http.StatusOK, model.UploadResponse{
 		Result:  true,
 		Message: message,
 		Data: &model.UploadData{
-			BillType:         billType,
-			FileURL:          fmt.Sprintf("/download/%s", outputFileName),
-			FileName:         outputFileName,
-			RawCount:         rawCount,
-			CleanedCount:     cleanedCount,
-			DuplicateCount:   dedupResult.DuplicateCount,
-			JDRelatedDeleted: jdRelatedDeleted,
+			BillType:              billType,
+			FileURL:               fmt.Sprintf("/download/%s", outputFileName),
+			FileName:              outputFileName,
+			RawCount:              rawCount,
+			CleanedCount:          cleanedCount,
+			DuplicateCount:        dedupResult.DuplicateCount,
+			JDRelatedDeleted:      jdRelatedDeleted,
+			ReconciledRefundCount: reconciledCount,
 		},
 	})
 }