feat: implement WeChat cross-batch refund reconciliation and fix misc issues

WeChat cross-batch refund reconciliation:
- Add OriginalAmount field to CleanedBill for accurate cumulative refund math
- DeduplicateRawFile detects WeChat status-update rows (已退款/已全额退款) and
  emits WechatRefundUpdates for Go-side reconciliation (Scenario 1)
- WechatPy cleaner surfaces -退款 income rows with no same-batch expense match
  as unresolved_refunds for Go ReconcileRefund (Scenario 2)
- Add ReconcileWechatRefund to repository interface and MongoDB implementation
- upload.go step 15 iterates WechatRefundUpdates and reconciles against bills_cleaned

Bug fixes:
- ReviewStats: add nil repo check to prevent panic when DB is not connected
- JWT: remove hardcoded fallback secret; return 500/401 if JWTSecret not configured
- Remove unused parsePageParam dead code and its strconv import
- BillDetailDrawer: show 不计收支 amount in muted gray instead of red
- test_jd_cleaner.py: replace hardcoded D:\Projects\BillAI path with dynamic __file__ resolution

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

server/service/bill.go

@@ -23,13 +23,21 @@ func getRepo() repository.BillRepository {
 	return repository.GetRepository()
 }
 
+// WechatRefundUpdate 微信重复行中携带的退款信息（用于跨批次退款核销）
+type WechatRefundUpdate struct {
+	TransactionID          string  // 原消费行的交易单号
+	FullRefund             bool    // 是否全额退款（已全额退款）
+	CumulativeRefundAmount float64 // 累计退款金额（已退款(¥X)中的 X，与原始金额相减得剩余）
+}
+
 // DeduplicateResult 去重结果
 type DeduplicateResult struct {
-	OriginalCount  int    // 原始记录数
-	DuplicateCount int    // 重复记录数
-	NewCount       int    // 新记录数
-	DedupFilePath  string // 去重后的文件路径（如果有去重则生成新文件）
-	BillType       string // 检测到的账单类型
+	OriginalCount       int                  // 原始记录数
+	DuplicateCount      int                  // 重复记录数
+	NewCount            int                  // 新记录数
+	DedupFilePath       string               // 去重后的文件路径（如果有去重则生成新文件）
+	BillType            string               // 检测到的账单类型
+	WechatRefundUpdates []WechatRefundUpdate // 微信重复行中检测到的退款状态（用于跨批次核销）
 }
 
 // DeduplicateRawFile 对原始文件进行去重检查，返回去重后的文件路径
@@ -75,6 +83,17 @@ func DeduplicateRawFile(filePath, uploadBatch string) (*DeduplicateResult, error
 		return result, nil
 	}
 
+	// 对于微信账单，找到"当前状态"列的索引，用于检测退款状态
+	wechatStatusIdx := -1
+	if billType == "wechat" {
+		for i, col := range header {
+			if col == "当前状态" {
+				wechatStatusIdx = i
+				break
+			}
+		}
+	}
+
 	// 检查每行是否重复
 	var newRows [][]string
 	for _, row := range dataRows {
@@ -101,6 +120,24 @@ func DeduplicateRawFile(filePath, uploadBatch string) (*DeduplicateResult, error
 			newRows = append(newRows, row)
 		} else {
 			result.DuplicateCount++
+			// 微信账单：检查重复行是否携带退款状态（跨批次退款核销）
+			if wechatStatusIdx >= 0 && len(row) > wechatStatusIdx {
+				status := strings.TrimSpace(row[wechatStatusIdx])
+				if strings.Contains(status, "已全额退款") {
+					result.WechatRefundUpdates = append(result.WechatRefundUpdates, WechatRefundUpdate{
+						TransactionID: transactionID,
+						FullRefund:    true,
+					})
+				} else if strings.Contains(status, "已退款") {
+					if amount := extractWechatRefundAmount(status); amount > 0 {
+						result.WechatRefundUpdates = append(result.WechatRefundUpdates, WechatRefundUpdate{
+							TransactionID:          transactionID,
+							FullRefund:             false,
+							CumulativeRefundAmount: amount,
+						})
+					}
+				}
+			}
 		}
 	}
 
@@ -337,6 +374,7 @@ func saveCleanedBillsFromCSV(filePath, billType, sourceFile, uploadBatch string)
 			bill.ReviewLevel = row[idx]
 		}
 
+		bill.OriginalAmount = bill.Amount
 		bills = append(bills, bill)
 	}
 
@@ -431,6 +469,7 @@ func saveCleanedBillsFromJSON(filePath, billType, sourceFile, uploadBatch string
 			bill.ReviewLevel = v
 		}
 
+		bill.OriginalAmount = bill.Amount
 		bills = append(bills, bill)
 	}
 
@@ -512,3 +551,28 @@ func parseAmount(s string) float64 {
 	}
 	return 0
 }
+
+// extractWechatRefundAmount 从微信"当前状态"字段中提取累计退款金额
+// 支持格式: "已退款(¥3.00)"、"已退款(￥3.00)"、"已退款￥3.00"
+func extractWechatRefundAmount(status string) float64 {
+	start := strings.Index(status, "(")
+	end := strings.LastIndex(status, ")")
+	var inner string
+	if start >= 0 && end > start {
+		inner = status[start+1 : end]
+	} else {
+		idx := strings.Index(status, "已退款")
+		if idx < 0 {
+			return 0
+		}
+		inner = status[idx+len("已退款"):]
+	}
+	inner = strings.TrimPrefix(inner, "¥")
+	inner = strings.TrimPrefix(inner, "￥")
+	inner = strings.TrimSpace(inner)
+	v, err := strconv.ParseFloat(inner, 64)
+	if err != nil {
+		return 0
+	}
+	return v
+}