fix: 系统检查修复 — 布局一致性 + bug 修复

- 公告图片样式统一：圆角 $radius-md，间距 $space-sm
- 首页紧急公告弹窗样式改为 SCSS 变量
- 新增 modal-mask-high mixin 统一高层级弹窗
- admin/config.vue 添加 initialLoaded 守卫避免重复请求
- notifications/index.vue 添加 initialLoaded 守卫
- notification store 所有方法添加 try-catch 错误处理

client/src/pages/index/index.vue

@@ -552,23 +552,14 @@ function goBills() {
 
 /* 强提醒公告弹窗 */
 .modal-mask {
-  position: fixed;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  background: rgba(0, 0, 0, 0.5);
-  z-index: 300;
-  display: flex;
-  align-items: center;
-  justify-content: center;
+  @include modal-mask-high;
 }
 
 .urgent-modal {
   width: 80%;
   max-height: 70vh;
-  background: #FFFFFF;
-  border-radius: 32rpx;
+  background: $surface;
+  border-radius: $radius-2xl;
   overflow: hidden;
   display: flex;
   flex-direction: column;
@@ -577,52 +568,52 @@ function goBills() {
 .urgent-header {
   display: flex;
   align-items: center;
-  gap: 12rpx;
-  padding: 32rpx 32rpx 16rpx;
+  gap: $space-sm;
+  padding: $space-xl $space-lg $space-md;
 }
 
 .urgent-title {
-  font-size: 32rpx;
+  font-size: $font-xl;
   font-weight: 600;
-  color: #2D1B1B;
+  color: $text;
   flex: 1;
 }
 
 .urgent-body {
   flex: 1;
-  padding: 0 32rpx 24rpx;
+  padding: 0 $space-lg $space-lg;
   max-height: 50vh;
 }
 
 .urgent-image {
   width: 100%;
-  border-radius: 16rpx;
-  margin-bottom: 16rpx;
+  border-radius: $radius-md;
+  margin-bottom: $space-sm;
 }
 
 .urgent-content {
-  font-size: 28rpx;
-  color: #2D1B1B;
+  font-size: $font-lg;
+  color: $text;
   line-height: 1.6;
 }
 
 .urgent-link {
-  margin-top: 16rpx;
-  padding: 12rpx 0;
+  margin-top: $space-sm;
+  padding: $space-xs 0;
 }
 
 .urgent-link-text {
-  font-size: 28rpx;
-  color: #FF8C69;
+  font-size: $font-lg;
+  color: $primary;
   text-decoration: underline;
 }
 
 .urgent-footer {
-  padding: 24rpx 32rpx;
-  border-top: 2rpx solid #F0E0D6;
+  padding: $space-lg;
+  border-top: 2rpx solid $border;
   text-align: center;
 
-  &:active { background: #FFF8F0; }
+  &:active { background: $surface-warm; }
 }
 
 .urgent-btn-text {