feat(ui): 重构核心 UI 组件库，新增 shadcn/ui 组件

- 重构 Button、Card、Badge、Input、Textarea 等基础组件
- 新增 Accordion、Alert、Dialog、Dropdown、Form 等 shadcn/ui 组件
- 新增 AnimatedCounter、StatsShowcase、MetricCard 等数据展示组件
- 新增 ScrollReveal 滚动动画组件
- 重构 Toast 通知系统与 Tooltip 提示组件
- 更新设计令牌系统，对齐新品牌视觉

src/components/ui/hover-card.tsx

@@ -0,0 +1,36 @@
+'use client';
+
+import * as React from 'react';
+import * as HoverCardPrimitive from '@radix-ui/react-hover-card';
+import { cn } from '@/lib/utils';
+
+/**
+ * 标准 shadcn/ui HoverCard 组件
+ * 基于 @radix-ui/react-hover-card
+ */
+const HoverCard = HoverCardPrimitive.Root;
+const HoverCardTrigger = HoverCardPrimitive.Trigger;
+
+const HoverCardContent = React.forwardRef<
+  React.ElementRef<typeof HoverCardPrimitive.Content>,
+  React.ComponentPropsWithoutRef<typeof HoverCardPrimitive.Content>
+>(({ className, align = 'center', sideOffset = 4, ...props }, ref) => (
+  <HoverCardPrimitive.Portal>
+    <HoverCardPrimitive.Content
+      ref={ref}
+      data-slot="hover-card-content"
+      align={align}
+      sideOffset={sideOffset}
+      className={cn(
+        'z-50 w-64 rounded-md border border-border-primary bg-bg-primary p-4 text-text-primary shadow-md outline-none',
+        'data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95',
+        'data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2',
+        className
+      )}
+      {...props}
+    />
+  </HoverCardPrimitive.Portal>
+));
+HoverCardContent.displayName = HoverCardPrimitive.Content.displayName;
+
+export { HoverCard, HoverCardTrigger, HoverCardContent };