Add JSON content extraction logic to DocumentsService

Added a new regex-based extraction method to handle JSON content wrapped in triple backticks, improving the robustness of content parsing. This ensures that JSON data is correctly identified and processed when present in the input string.

Author: 239573049

src/KoalaWiki/KoalaWarehouse/DocumentsService.cs

@@ -223,6 +223,19 @@ await dbContext.DocumentOverviews.AddAsync(new DocumentOverview()
                     str.Clear();
                     str.Append(extractedContent);
                 }
+                else
+                {
+                    // 尝试使用```json
+                    var jsonRegex = new Regex(@"```json(.*?)```", RegexOptions.Singleline);
+                    var jsonMatch = jsonRegex.Match(str.ToString());
+                    if (jsonMatch.Success)
+                    {
+                        // 提取到的内容
+                        var extractedContent = jsonMatch.Groups[1].Value;
+                        str.Clear();
+                        str.Append(extractedContent);
+                    }
+                }
 
                 try
                 {