Web 前端新增暗夜模式切换

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/frontend/src/views/AdminUsersView.vue

@@ -193,6 +193,6 @@ onMounted(reload)
   display: flex;
   justify-content: space-between;
   align-items: center;
-  color: #606266;
+  color: var(--el-text-color-regular);
 }
 </style>

web/frontend/src/views/LoginView.vue

@@ -69,7 +69,8 @@ async function submit() {
 .card {
   width: 360px;
   padding: 36px 32px;
-  background: #fff;
+  background: var(--el-bg-color);
+  color: var(--el-text-color-primary);
   border-radius: 8px;
   box-shadow: 0 12px 32px rgba(0, 0, 0, 0.18);
 }
@@ -79,7 +80,7 @@ async function submit() {
 }
 .hint {
   margin: 0 0 24px;
-  color: #909399;
+  color: var(--el-text-color-secondary);
   font-size: 12px;
   text-align: center;
 }

web/frontend/src/views/ScoresView.vue

@@ -120,6 +120,6 @@ onMounted(async () => {
   padding: 12px 16px;
 }
 .score-table {
-  background: #fff;
+  background: var(--el-bg-color);
 }
 </style>