feat: 添加应用图标搜索功能及相关页面

新增应用图标搜索功能，包括搜索表单、图标展示、加载更多和返回顶部按钮。页面结构、样式和交互逻辑均已实现。

old/css/styles.css

@@ -0,0 +1,125 @@
+body {
+    font-family: 'Roboto', sans-serif;
+    background-color: #f0f2f5;
+    color: #333;
+    margin: 0;
+    padding: 0;
+}
+
+.container {
+    max-width: 800px;
+    margin: 0 auto;
+    padding: 20px;
+    text-align: center;
+}
+
+h1 {
+    color: #444;
+}
+
+form {
+    margin-bottom: 20px;
+}
+
+input[type="text"] {
+    padding: 10px;
+    width: 70%;
+    border: 1px solid #ccc;
+    border-radius: 5px;
+}
+
+button {
+    padding: 10px 20px;
+    background-color: #007bff;
+    color: white;
+    border: none;
+    border-radius: 5px;
+    cursor: pointer;
+    transition: background-color 0.3s ease;
+}
+
+button:hover {
+    background-color: #0056b3;
+}
+
+.icon-grid {
+    display: grid;
+    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
+    gap: 20px;
+    justify-items: center;
+}
+
+.icon-grid div {
+    flex: 1 1 calc(25% - 20px);
+    text-align: center;
+}
+
+.icon-grid img {
+    max-width: 120px;
+    border-radius: 15px;
+    transition: transform 0.3s ease;
+}
+
+.icon-grid img:hover {
+    transform: scale(1.1);
+}
+/* 返回顶部按钮 */
+#back-to-top {
+    position: fixed;
+    bottom: 40px;
+    right: 20px;
+    display: none;
+    width: 50px;
+    height: 50px;
+    background-color: #007bff;
+    color: white;
+    border: none;
+    border-radius: 50%;
+    font-size: 24px;
+    cursor: pointer;
+    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
+    transition: background-color 0.3s ease;
+}
+
+#back-to-top:hover {
+    background-color: #0056b3;
+}
+
+/* 页脚样式 */
+footer {
+    background-color: #333;
+    color: white;
+    padding: 20px 0;
+    text-align: center;
+}
+
+.footer-content {
+    max-width: 800px;
+    margin: 0 auto;
+}
+
+.footer-content p {
+    font-size: 18px;
+    margin-bottom: 10px;
+}
+
+.footer-content ul {
+    list-style-type: none;
+    padding: 0;
+    margin: 0;
+    display: flex;
+    justify-content: center;
+}
+
+.footer-content ul li {
+    margin: 0 15px;
+}
+
+.footer-content ul li a {
+    color: white;
+    text-decoration: none;
+}
+
+.footer-content ul li a:hover {
+    text-decoration: underline;
+}