feat(theme): 更新设计系统至v3.0并优化UI组件

- 升级主题系统为SionRUI AI创意设计系统v3.0，采用蓝紫科技色调
- 优化TopNav组件，改进毛玻璃效果和边框样式
- 增强VideoPreviewModal的视频预览布局和响应式设计
- 重构IdentifyFace页面，使用shadcn主题和Tailwind风格
- 更新Benchmark相关组件，统一使用设计系统颜色变量
- 移除Agents页面多余的边框样式
- 改进深色模式配色方案，增强霓虹科技感

frontend/app/web-gold/src/components/TopNav.vue

@@ -18,7 +18,8 @@ const shouldShowUser = computed(() => {
 
 <template>
   <header
-    class="p-1 fixed top-0 left-0 right-0 flex items-center px-6 h-[70px] bg-background/95 backdrop-blur-sm border-b border-border z-50"
+    class="p-1 fixed top-0 left-0 right-0 flex items-center px-6 h-[70px] bg-background/80 border-b border-border/50 z-50"
+    style="backdrop-filter: blur(12px)"
   >
     <div class="flex items-center gap-4 flex-1">
       <BrandLogo :size="36" />
@@ -40,6 +41,10 @@ const shouldShowUser = computed(() => {
 </template>
 
 <style scoped>
+header {
+  backdrop-filter: blur(12px);
+}
+
 .theme-toggle {
   display: flex;
   align-items: center;

frontend/app/web-gold/src/components/VideoPreviewModal.vue

@@ -63,6 +63,8 @@ const handleClose = () => {
   max-height: 90vh;
   border-radius: var(--radius-lg);
   overflow: hidden;
+  display: flex;
+  flex-direction: column;
 }
 
 .video-container {
@@ -71,14 +73,18 @@ const handleClose = () => {
   align-items: center;
   justify-content: center;
   padding: 0;
+  overflow: hidden;
+  flex: 1;
+  min-height: 0;
 }
 
 .preview-video {
-  max-width: 800px;
-  max-height: 70vh;
+  max-width: 100%;
+  max-height: 100%;
   width: auto;
   height: auto;
   display: block;
+  object-fit: contain;
 }
 
 // 响应式：小屏幕