feat: 优化首页设计并添加回到顶部按钮

✨ 首页优化：
- 丰富项目介绍内容，增加平台特色说明
- 新增平台优势展示区域（AI智能分析、专业可靠、高效便捷、趋势对比）
- 添加平台数据统计展示（10+核心算法、99%准确率、24/7服务、100%隐私保护）
- 新增技术特色介绍（AI智能优化、算法精进）
- 优化CTA区域，提供更清晰的行动引导
- 改进功能描述，突出技术优势

� 回到顶部功能：
- 创建BackToTop通用组件，支持半透明浮动设计
- 集成到所有分析结果页面（八字、紫微、易经）
- 智能显示/隐藏机制（滚动300px后显示）
- 平滑滚动动画和悬停效果
- 中国风配色方案，与整体设计保持一致

� 用户体验提升：
- 首页内容更加丰富专业，提升用户信任度
- 长页面导航体验优化，便于用户快速返回顶部
- 保持设计风格一致性，提升整体视觉效果

src/components/CompleteBaziAnalysis.tsx

@@ -2,6 +2,7 @@ import React, { useState, useEffect } from 'react';
 import { Radar, RadarChart, PolarGrid, PolarAngleAxis, PolarRadiusAxis, ResponsiveContainer } from 'recharts';
 import { Calendar, Star, BookOpen, Sparkles, User, BarChart3, Zap, TrendingUp, Loader2, Clock, Target, Heart, DollarSign, Activity } from 'lucide-react';
 import { Card, CardContent, CardHeader, CardTitle } from './ui/Card';
+import { BackToTop } from './ui/BackToTop';
 import { localApi } from '../lib/localApi';
 
 interface CompleteBaziAnalysisProps {
@@ -1031,6 +1032,9 @@ const CompleteBaziAnalysis: React.FC<CompleteBaziAnalysisProps> = ({ birthDate,
           </CardContent>
         </Card>
       </div>
+      
+      {/* 回到顶部按钮 */}
+      <BackToTop />
     </div>
   );
 };

src/components/CompleteYijingAnalysis.tsx

@@ -1,6 +1,7 @@
 import React, { useState, useEffect } from 'react';
 import { Calendar, Star, BookOpen, Sparkles, User, BarChart3, Zap, TrendingUp, Loader2, Clock, Target, Heart, DollarSign, Activity, Crown, Compass, Moon, Sun, Hexagon, Layers, Eye, Shuffle } from 'lucide-react';
 import { Card, CardContent, CardHeader, CardTitle } from './ui/Card';
+import { BackToTop } from './ui/BackToTop';
 import { localApi } from '../lib/localApi';
 
 interface CompleteYijingAnalysisProps {
@@ -734,6 +735,9 @@ const CompleteYijingAnalysis: React.FC<CompleteYijingAnalysisProps> = ({
           </CardContent>
         </Card>
       </div>
+      
+      {/* 返回顶部按钮 */}
+      <BackToTop />
     </div>
   );
 };

src/components/CompleteZiweiAnalysis.tsx

@@ -4,6 +4,7 @@ import { Calendar, Star, BookOpen, Sparkles, User, BarChart3, Zap, TrendingUp, L
 import { Card, CardContent, CardHeader, CardTitle } from './ui/Card';
 import { ChineseCard, ChineseCardContent, ChineseCardHeader, ChineseCardTitle } from './ui/ChineseCard';
 import { ChineseLoading } from './ui/ChineseLoading';
+import { BackToTop } from './ui/BackToTop';
 import { localApi } from '../lib/localApi';
 import { cn } from '../lib/utils';
 
@@ -1550,6 +1551,9 @@ const CompleteZiweiAnalysis: React.FC<CompleteZiweiAnalysisProps> = ({ birthDate
           </CardContent>
         </Card>
       </div>
+      
+      {/* 回到顶部按钮 */}
+      <BackToTop />
     </div>
   );
 };

src/components/ui/BackToTop.tsx

@@ -0,0 +1,75 @@
+import React, { useState, useEffect } from 'react';
+import { ChevronUp } from 'lucide-react';
+import { cn } from '../../lib/utils';
+
+interface BackToTopProps {
+  className?: string;
+  threshold?: number; // 滚动多少像素后显示按钮
+}
+
+const BackToTop: React.FC<BackToTopProps> = ({ 
+  className,
+  threshold = 300 
+}) => {
+  const [isVisible, setIsVisible] = useState(false);
+
+  // 监听滚动事件
+  useEffect(() => {
+    const toggleVisibility = () => {
+      if (window.pageYOffset > threshold) {
+        setIsVisible(true);
+      } else {
+        setIsVisible(false);
+      }
+    };
+
+    window.addEventListener('scroll', toggleVisibility);
+
+    return () => {
+      window.removeEventListener('scroll', toggleVisibility);
+    };
+  }, [threshold]);
+
+  // 滚动到顶部
+  const scrollToTop = () => {
+    window.scrollTo({
+      top: 0,
+      behavior: 'smooth'
+    });
+  };
+
+  if (!isVisible) {
+    return null;
+  }
+
+  return (
+    <button
+      onClick={scrollToTop}
+      className={cn(
+        // 基础样式
+        'fixed bottom-6 right-6 z-50',
+        'w-12 h-12 rounded-full',
+        'flex items-center justify-center',
+        'transition-all duration-300 ease-in-out',
+        'shadow-lg hover:shadow-xl',
+        // 中国风配色
+        'bg-red-600/80 hover:bg-red-700/90',
+        'border-2 border-yellow-400/50 hover:border-yellow-300/70',
+        'backdrop-blur-sm',
+        // 动画效果
+        'transform hover:scale-110 active:scale-95',
+        'hover:-translate-y-1',
+        className
+      )}
+      aria-label="回到顶部"
+      title="回到顶部"
+    >
+      <ChevronUp 
+        className="w-6 h-6 text-yellow-100 hover:text-yellow-50 transition-colors" 
+      />
+    </button>
+  );
+};
+
+export default BackToTop;
+export { BackToTop };