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/flip-clock.tsx

@@ -20,12 +20,12 @@ function FlipDigit({ digit, prevDigit }: FlipDigitProps) {
       {/* 背景卡片 - 静态显示当前数字 */}
       <div className="absolute inset-0 bg-gradient-to-b from-[var(--color-bg-primary)] via-[var(--color-bg-primary)] to-[var(--color-flip-card-bg)] rounded-lg shadow-xl overflow-hidden border border-[var(--color-flip-card-border)]">
         <div className="absolute top-0 left-0 right-0 h-1/2 bg-gradient-to-b from-[var(--color-bg-primary)] to-[var(--color-flip-card-bg)] border-b border-[var(--color-flip-card-border)] overflow-hidden">
-          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand-primary)]">
+          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand)]">
             {digit}
           </div>
         </div>
         <div className="absolute bottom-0 left-0 right-0 h-1/2 bg-gradient-to-b from-[var(--color-bg-primary)] to-[var(--color-flip-card-bg)] overflow-hidden">
-          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand-primary)]">
+          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand)]">
             {digit}
           </div>
         </div>
@@ -46,7 +46,7 @@ function FlipDigit({ digit, prevDigit }: FlipDigitProps) {
             backfaceVisibility: 'hidden',
           }}
         >
-          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand-primary)]">
+          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand)]">
             {prevDigit}
           </div>
         </motion.div>
@@ -64,7 +64,7 @@ function FlipDigit({ digit, prevDigit }: FlipDigitProps) {
             backfaceVisibility: 'hidden',
           }}
         >
-          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand-primary)]">
+          <div className="absolute inset-0 flex items-center justify-center text-4xl sm:text-5xl md:text-6xl font-bold text-[var(--color-brand)]">
             {digit}
           </div>
         </motion.div>
@@ -134,9 +134,9 @@ export function FlipClock({ years, months, days }: FlipClockProps) {
       
       <div className="flex flex-wrap justify-center items-center gap-4 sm:gap-6 mb-6">
         <FlipCard value={years} label="年" maxDigits={2} />
-        <div className="text-2xl sm:text-3xl font-bold text-[var(--color-brand-primary)]">:</div>
+        <div className="text-2xl sm:text-3xl font-bold text-[var(--color-brand)]">:</div>
         <FlipCard value={months} label="个月" maxDigits={2} />
-        <div className="text-2xl sm:text-3xl font-bold text-[var(--color-brand-primary)]">:</div>
+        <div className="text-2xl sm:text-3xl font-bold text-[var(--color-brand)]">:</div>
         <FlipCard value={days} label="天" maxDigits={3} />
       </div>