添加扫码登录功能，新增登录API接口，更新前端页面和样式，删除不必要的文件。

static/css/style.css

@@ -0,0 +1,108 @@
+* {
+    margin: 0;
+    padding: 0;
+    box-sizing: border-box;
+}
+
+body {
+    font-family: 'PingFang SC', 'Microsoft YaHei', sans-serif;
+    background-color: #f5f5f5;
+    color: #333;
+}
+
+.container {
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    min-height: 100vh;
+    padding: 20px;
+}
+
+.login-box {
+    background-color: #fff;
+    border-radius: 10px;
+    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
+    padding: 30px;
+    width: 100%;
+    max-width: 400px;
+    text-align: center;
+}
+
+h1 {
+    margin-bottom: 30px;
+    color: #1e88e5;
+    font-size: 24px;
+}
+
+.scan-area {
+    position: relative;
+    width: 100%;
+    height: 300px;
+    margin-bottom: 20px;
+    border: 1px solid #e0e0e0;
+    border-radius: 8px;
+    overflow: hidden;
+    background-color: #f9f9f9;
+}
+
+#camera-container {
+    width: 100%;
+    height: 100%;
+}
+
+#video {
+    width: 100%;
+    height: 100%;
+    object-fit: cover;
+}
+
+#scan-placeholder {
+    display: flex;
+    flex-direction: column;
+    justify-content: center;
+    align-items: center;
+    height: 100%;
+}
+
+#scan-placeholder img {
+    width: 80px;
+    height: 80px;
+    margin-bottom: 20px;
+}
+
+.btn {
+    background-color: #1e88e5;
+    color: white;
+    border: none;
+    border-radius: 5px;
+    padding: 12px 20px;
+    font-size: 16px;
+    cursor: pointer;
+    transition: background-color 0.3s;
+    width: 100%;
+    margin-top: 10px;
+}
+
+.btn:hover {
+    background-color: #1976d2;
+}
+
+#stop-button {
+    background-color: #e53935;
+}
+
+#stop-button:hover {
+    background-color: #d32f2f;
+}
+
+#scan-result {
+    padding: 20px;
+    text-align: center;
+}
+
+#result-content {
+    margin-top: 10px;
+    word-break: break-all;
+    font-size: 14px;
+    color: #1e88e5;
+}