style(dnfs): 打磨首页 index 视觉细节，保持朴素风格

static/public/index.html

@@ -13,7 +13,10 @@
 </head>
 <body>
     <header class="header">
-        <h1 id="logo">DNFS 树状笔记</h1>
+        <h1 id="logo">
+            <svg viewBox="0 0 24 24" width="16" height="16" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="vertical-align:-2px;margin-right:6px;color:var(--accent)"><circle cx="18" cy="5" r="3"/><circle cx="6" cy="12" r="3"/><circle cx="18" cy="19" r="3"/><line x1="8.59" y1="10.51" x2="15.42" y2="6.51"/><line x1="8.59" y1="13.49" x2="15.42" y2="17.49"/></svg>
+            DNFS 树状笔记
+        </h1>
         <nav class="right-group" aria-label="用户操作">
             <img src="favicon.ico" alt="用户头像" id="avatar" style="display:none">
             <b id="name" style="display:none"></b>