feat: add serveStatic middleware

public/index.html

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+<!DOCTYPE html>
+<html lang="zh-CN">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>V-Hono 静态文件服务 - Public 目录</title>
+    <style>
+        body { 
+            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; 
+            max-width: 600px; 
+            margin: 50px auto; 
+            padding: 20px; 
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            color: white;
+            text-align: center;
+        }
+        .container {
+            background: rgba(255, 255, 255, 0.1);
+            padding: 30px;
+            border-radius: 15px;
+            backdrop-filter: blur(10px);
+            box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
+        }
+        h1 { margin-bottom: 20px; font-size: 2.5em; }
+        p { font-size: 1.2em; line-height: 1.6; }
+        .feature { 
+            background: rgba(255, 255, 255, 0.2); 
+            padding: 15px; 
+            margin: 10px 0; 
+            border-radius: 8px; 
+        }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <h1>🎉 成功！</h1>
+        <p>这是来自 <code>./public</code> 目录的 <code>index.html</code> 文件</p>
+        
+        <div class="feature">
+            <h3>✨ V-Hono 静态文件服务特性</h3>
+            <p>✅ 自动索引文件支持</p>
+            <p>✅ 路径遍历攻击防护</p>
+            <p>✅ ETag 和缓存支持</p>
+            <p>✅ 智能 Content-Type 检测</p>
+        </div>
+        
+        <p><a href="/" style="color: #fff; text-decoration: underline;">← 返回主页</a></p>
+    </div>
+</body>
+</html> 

public/test.txt

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+Hello from V-Hono static file server!
+
+This is a test file from the ./public directory.
+You can access this file directly via the root path (/).
+
+Features demonstrated:
+- Text file serving
+- Content-Type detection
+- Path mapping from URL to file system