fix: remove forced transparent background from code elements and fix JSX tag mismatch

- remove [&_code]:!bg-transparent and [&_code]:!p-0 classes from ChatInterface.jsx
- fix div/span closing tag mismatch in CodeBlock.jsx

Author: kei9o

src/components/ChatInterface.jsx

@@ -727,7 +727,7 @@ const MessageComponent = memo(({ message, index, prevMessage, createDiff, onFile
             ) : (
               <div className="text-sm text-gray-700 dark:text-gray-300">
                 {message.type === 'assistant' ? (
-                  <div className="prose prose-sm max-w-none dark:prose-invert prose-gray [&_code]:!bg-transparent [&_code]:!p-0">
+                  <div className="prose prose-sm max-w-none dark:prose-invert prose-gray">
                     <ReactMarkdown
                       components={{
                         code: MarkdownCodeBlock,

src/components/CodeBlock.jsx

@@ -105,7 +105,7 @@ const CodeBlock = memo(({
       >
         {code}
       </SyntaxHighlighter>
-    </span>
+    </div>
   );
 
   return codeBlock;