feat: 官方等价对比改为轮播动效，展示所有匹配模型

- 新增 RotatingEquiv 组件，3秒间隔淡入淡出切换
- calcOfficialEquivList 返回所有匹配模型（含 Gemini 系列）
- Packages 页面和 7 个 Home 模板全部适配轮播

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/bits/RotatingEquiv.jsx

@@ -0,0 +1,34 @@
+import React, { useState, useEffect } from 'react';
+
+/**
+ * Rotating display of official price equivalents.
+ * Cycles through items with a fade up/down transition.
+ *
+ * @param {{ items: {label:string, equivDollars:number}[], text: (item) => string, className?: string, interval?: number }}
+ */
+export default function RotatingEquiv({ items, text, className = '', interval = 3000 }) {
+  const [idx, setIdx] = useState(0);
+  const [visible, setVisible] = useState(true);
+
+  useEffect(() => {
+    if (items.length <= 1) return;
+    const timer = setInterval(() => {
+      setVisible(false);
+      setTimeout(() => {
+        setIdx((i) => (i + 1) % items.length);
+        setVisible(true);
+      }, 300);
+    }, interval);
+    return () => clearInterval(timer);
+  }, [items.length, interval]);
+
+  if (!items || items.length === 0) return null;
+
+  return (
+    <span
+      className={`inline-block transition-all duration-300 ${visible ? 'opacity-100 translate-y-0' : 'opacity-0 translate-y-1'} ${className}`}
+    >
+      {text(items[idx])}
+    </span>
+  );
+}