feat(website): 三轮视觉改造与页面过渡动画

改造概要（30项）：
- 第一轮：Hero重构/Section差异化/SocialProof强化/CTA对比度/About架构
- 第二轮：字体优化/背景交替/Solutions差异化/Footer五列/MegaDropdown修复
- 第三轮：卡片交互/表单层级/CTA统一/时间线标记/连接线/三列布局/移动导航/Button微交互/SEO Schema
- P3-2：template.tsx+Framer Motion页面过渡/loading.tsx加载状态
- 清理：删除未用组件/hooks，修复重复移动导航，清理冗余CSS

src/components/ui/card.tsx

@@ -7,7 +7,7 @@ function Card({ className, ...props }: React.ComponentProps<"div">) {
     <div
       data-slot="card"
       className={cn(
-        "bg-[#FAFAFA] text-[#1C1C1C] flex flex-col gap-6 rounded-xl border border-[#E5E5E5] py-6 shadow-[0_2px_8px_rgba(0,0,0,0.04)] transition-all duration-300 hover:border-[#1C1C1C] hover:shadow-[0_8px_24px_rgba(0,0,0,0.06)] hover:-translate-y-1",
+        "bg-[var(--color-bg-section)] text-[var(--color-text-primary)] flex flex-col gap-6 rounded-xl border border-[var(--color-border-primary)] py-6 shadow-[0_2px_8px_rgba(0,0,0,0.04)] transition-all duration-300 hover:border-[var(--color-primary)] hover:shadow-[0_8px_24px_rgba(0,0,0,0.06)] hover:-translate-y-1",
         className
       )}
       {...props}
@@ -32,7 +32,7 @@ function CardTitle({ className, ...props }: React.ComponentProps<"div">) {
   return (
     <div
       data-slot="card-title"
-      className={cn("leading-none font-semibold text-[#1C1C1C]", className)}
+      className={cn("leading-none font-semibold text-[var(--color-text-primary)]", className)}
       {...props}
     />
   )
@@ -42,7 +42,7 @@ function CardDescription({ className, ...props }: React.ComponentProps<"div">) {
   return (
     <div
       data-slot="card-description"
-      className={cn("text-[#5C5C5C] text-sm", className)}
+      className={cn("text-[var(--color-text-placeholder)] text-sm", className)}
       {...props}
     />
   )
@@ -75,7 +75,7 @@ function CardFooter({ className, ...props }: React.ComponentProps<"div">) {
   return (
     <div
       data-slot="card-footer"
-      className={cn("flex items-center px-6 [.border-t]:pt-6 border-t border-[#E5E5E5]", className)}
+      className={cn("flex items-center px-6 [.border-t]:pt-6 border-t border-[var(--color-border-primary)]", className)}
       {...props}
     />
   )