fix: 修复侧边栏 Logo 加载时的闪烁问题

- 添加 settingsLoaded 条件判断，确保公共设置加载完成后再显示 Logo
- 避免在设置未加载时显示默认 Logo 造成的闪烁效果

frontend/src/components/layout/AppSidebar.vue

@@ -9,7 +9,7 @@
     <!-- Logo/Brand -->
     <div class="sidebar-header">
       <!-- Custom Logo or Default Logo -->
-      <div class="flex h-9 w-9 items-center justify-center overflow-hidden rounded-xl shadow-glow">
+      <div v-if="settingsLoaded" class="flex h-9 w-9 items-center justify-center overflow-hidden rounded-xl shadow-glow">
         <img :src="siteLogo || '/logo.png'" alt="Logo" class="h-full w-full object-contain" />
       </div>
       <transition name="fade">
@@ -167,6 +167,7 @@ const isDark = ref(document.documentElement.classList.contains('dark'))
 const siteName = computed(() => appStore.siteName)
 const siteLogo = computed(() => appStore.siteLogo)
 const siteVersion = computed(() => appStore.siteVersion)
+const settingsLoaded = computed(() => appStore.publicSettingsLoaded)
 
 // SVG Icon Components
 const DashboardIcon = {