improvement(entry-ui): 优化检测与导入首屏流程

- 重构检测结果页布局，补充版本/账号/数据库统计与更清晰的加载态

- 首页移除直接解密入口，/import 页面隐藏侧边栏，统一首屏使用路径

- 导入页优化预览、错误和重试体验，并补充 SSE 连接清理逻辑

Author: 2977094657

frontend/app.vue

@@ -101,7 +101,7 @@ const showDesktopTitleBar = computed(() => isDesktop.value)
 
 const showSidebar = computed(() => {
   const path = String(route.path || '')
-  if (path === '/') return false
+  if (path === '/' || path === '/import') return false
   if (path === '/decrypt' || path === '/detection-result' || path === '/decrypt-result') return false
   return !(path === '/wrapped' || path.startsWith('/wrapped/'))
 })