feat: 添加图标和路由配置

- 新增多个 SVG 图标文件
- 添加 `/demo/icons` 路由配置，用于图标预览

src/assets/svg/xt-account.svg

@@ -0,0 +1,8 @@
+<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <path
+    d="M16.75 12C17.1642 12 17.5 12.3358 17.5 12.75C17.5 13.1642 17.1642 13.5 16.75 13.5C16.3358 13.5 16 13.1642 16 12.75C16 12.3358 16.3358 12 16.75 12Z"
+    fill="currentColor"/>
+  <path fill-rule="evenodd" clip-rule="evenodd"
+        d="M13.5 2.5C14.0537 2.5 14.9195 2.67544 15.667 3.29102C16.269 3.78688 16.726 4.5139 16.9102 5.5H20.5C21.6046 5.5 22.5 6.39543 22.5 7.5V18.5C22.5 19.6046 21.6046 20.5 20.5 20.5H3.5C2.39543 20.5 1.5 19.6046 1.5 18.5V7.5C1.5 6.56722 2.1391 5.78564 3.00293 5.56445C3.01903 5.042 3.1831 4.32538 3.65137 3.7041C4.18192 3.00021 5.04297 2.5 6.25 2.5H13.5ZM3.5 18.5H20.5V16.5H12.5C11.9477 16.5 11.5 16.0523 11.5 15.5V10C11.5 9.44772 11.9477 9 12.5 9H20.5V7.5H3.5V18.5ZM13.5 14.5H20.5V11H13.5V14.5ZM6.25 4.5C5.65705 4.5 5.39347 4.71657 5.24902 4.9082C5.11038 5.09214 5.03894 5.31915 5.0127 5.5H14.8447C14.7232 5.16558 14.5511 4.96212 14.3955 4.83398C14.0805 4.57472 13.6963 4.5 13.5 4.5H6.25Z"
+        fill="currentColor"/>
+</svg>