fix: escape Telegram Markdown special characters (fix #450)

app/Services/TelegramService.php

@@ -29,7 +29,9 @@ class TelegramService
 
     public function sendMessage(int $chatId, string $text, string $parseMode = ''): void
     {
-        $text = $parseMode === 'markdown' ? str_replace('_', '\_', $text) : $text;
+        if ($parseMode === 'markdown') {
+            $text = $this->escapeMarkdown($text);
+        }
 
         $this->request('sendMessage', [
             'chat_id' => $chatId,
@@ -38,6 +40,26 @@ class TelegramService
         ]);
     }
 
+    /**
+     * 转义 Telegram Markdown 特殊字符
+     */
+    protected function escapeMarkdown(string $text): string
+    {
+        $escapeChars = ['_', '*', '`', '['];
+        $escapedText = '';
+        
+        for ($i = 0; $i < strlen($text); $i++) {
+            $char = $text[$i];
+            if (in_array($char, $escapeChars, true)) {
+                $escapedText .= '\\' . $char;
+            } else {
+                $escapedText .= $char;
+            }
+        }
+        
+        return $escapedText;
+    }
+
     public function approveChatJoinRequest(int $chatId, int $userId): void
     {
         $this->request('approveChatJoinRequest', [