feat: 移除未使用的消息处理函数和Markdown插件任务创建功能，优化代码结构

app/Models/WebSocketDialogMsg.php

@@ -695,7 +695,6 @@ class WebSocketDialogMsg extends AbstractModel
                 $text = $title;
             } else {
                 $text = Base::markdown2html($text);
-                $text = self::previewConvertTaskList($text);
             }
         }
         $text = preg_replace("/<img\s+class=\"emoticon\"[^>]*?alt=\"(\S+)\"[^>]*?>/", "[$1]", $text);
@@ -711,36 +710,6 @@ class WebSocketDialogMsg extends AbstractModel
         return $text;
     }
 
-    /**
-     * 转换任务列表
-     * @param $text
-     * @return array|string|string[]|null
-     */
-    private static function previewConvertTaskList($text) {
-        $pattern = '/:::\s*(create-task-list|create-subtask-list)(.*?):::/s';
-        $replacement = function($matches) {
-            $content = $matches[2];
-            $lines = explode("\n", trim($content));
-            $result = [];
-            $currentTitle = '';
-            foreach ($lines as $line) {
-                $line = trim($line);
-                if (empty($line)) continue;
-
-                if (preg_match('/^title:\s*(.+)$/', $line, $titleMatch)) {
-                    $currentTitle = $titleMatch[1];
-                    $result[] = $currentTitle;
-                } elseif (preg_match('/^desc:\s*(.+)$/', $line, $descMatch)) {
-                    if (!empty($currentTitle)) {
-                        $result[] = $descMatch[1];
-                    }
-                }
-            }
-            return implode("\n", $result);
-        };
-        return preg_replace_callback($pattern, $replacement, $text);
-    }
-
     /**
      * 预览文件消息
      * @param $msg