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>

analyzer/server.py

@@ -52,6 +52,7 @@ class CleanResponse(BaseModel):
     bill_type: str
     message: str
     output_path: Optional[str] = None
+    unresolved_refunds: list[dict] = []
 
 
 class CategoryRequest(BaseModel):
@@ -138,27 +139,27 @@ def do_clean(
     start: str = None,
     end: str = None,
     output_format: str = "csv"
-) -> tuple[bool, str, str]:
+) -> tuple[bool, str, str, list[dict]]:
     """
     执行清洗逻辑
-    
+
     Returns:
-        (success, bill_type, message)
+        (success, bill_type, message, unresolved_refunds)
     """
     # 检查文件是否存在
     if not Path(input_path).exists():
-        return False, "", f"文件不存在: {input_path}"
-    
+        return False, "", f"文件不存在: {input_path}", []
+
     # 检测账单类型
     if bill_type == "auto":
         detected_type = detect_bill_type(input_path)
         if detected_type is None:
-            return False, "", "无法识别账单类型"
+            return False, "", "无法识别账单类型", []
         bill_type = detected_type
-    
+
     # 计算日期范围
     start_date, end_date = compute_date_range_from_values(year, month, start, end)
-    
+
     # 创建对应的清理器
     try:
         if bill_type == "alipay":
@@ -167,15 +168,15 @@ def do_clean(
             cleaner = JDCleaner(input_path, output_path, output_format)
         else:
             cleaner = WechatCleaner(input_path, output_path, output_format)
-        
+
         cleaner.set_date_range(start_date, end_date)
         cleaner.clean()
-        
+
         type_names = {"alipay": "支付宝", "wechat": "微信", "jd": "京东白条"}
-        return True, bill_type, f"✅ {type_names.get(bill_type, bill_type)}账单清洗完成"
-    
+        return True, bill_type, f"✅ {type_names.get(bill_type, bill_type)}账单清洗完成", cleaner.unresolved_refunds
+
     except Exception as e:
-        return False, bill_type, f"清洗失败: {str(e)}"
+        return False, bill_type, f"清洗失败: {str(e)}", []
 
 
 # =============================================================================
@@ -215,7 +216,7 @@ async def clean_bill(request: CleanRequest):
     
     接收账单文件路径，执行清洗后输出到指定路径
     """
-    success, bill_type, message = do_clean(
+    success, bill_type, message, unresolved_refunds = do_clean(
         input_path=request.input_path,
         output_path=request.output_path,
         bill_type=request.bill_type or "auto",
@@ -225,15 +226,16 @@ async def clean_bill(request: CleanRequest):
         end=request.end,
         output_format=request.format or "csv"
     )
-    
+
     if not success:
         raise HTTPException(status_code=400, detail=message)
-    
+
     return CleanResponse(
         success=True,
         bill_type=bill_type,
         message=message,
-        output_path=request.output_path
+        output_path=request.output_path,
+        unresolved_refunds=unresolved_refunds
     )
 
 
@@ -264,7 +266,7 @@ async def clean_bill_upload(
         output_path = tmp_output.name
     
     try:
-        success, detected_type, message = do_clean(
+        success, detected_type, message, unresolved_refunds = do_clean(
             input_path=input_path,
             output_path=output_path,
             bill_type=bill_type or "auto",
@@ -274,15 +276,16 @@ async def clean_bill_upload(
             end=end,
             output_format=format or "csv"
         )
-        
+
         if not success:
             raise HTTPException(status_code=400, detail=message)
-        
+
         return CleanResponse(
             success=True,
             bill_type=detected_type,
             message=message,
-            output_path=output_path
+            output_path=output_path,
+            unresolved_refunds=unresolved_refunds
         )
     
     finally: