fix(breadcrumb): 修复移动端面包屑垂直对齐问题

根本原因：元素padding不一致导致高度差异
- Home图标: p-1.5 → 高度28px
- 文字链接: py-1 → 高度22px
- 结果：垂直不对齐，看起来"歪"

修复内容：
- 移除所有不对称的padding
- 统一使用gap-2间距
- 箭头颜色从#E5E5E5改为#CCCCCC（更可见）
- 箭头大小调整为w-3.5 h-3.5

src/components/layout/breadcrumb.tsx

@@ -14,20 +14,20 @@ interface BreadcrumbProps {
 
 export function Breadcrumb({ items }: BreadcrumbProps) {
   return (
-    <nav aria-label="breadcrumb" className="flex items-center gap-1.5 text-xs md:text-sm text-[#5C5C5C] py-3 md:py-4">
+    <nav aria-label="breadcrumb" className="flex items-center gap-2 text-xs md:text-sm text-[#5C5C5C] py-3 md:py-4">
       <StaticLink 
         href="/" 
-        className="inline-flex items-center hover:text-[#C41E3A] transition-colors p-1.5 rounded" 
+        className="inline-flex items-center hover:text-[#C41E3A] transition-colors" 
         aria-label="返回首页"
       >
         <Home className="w-4 h-4" />
       </StaticLink>
       {items.map((item, index) => (
         <div key={index} className="flex items-center">
-          <ChevronRight className="w-4 h-4 text-[#E5E5E5] mx-0.5" />
+          <ChevronRight className="w-3.5 h-3.5 text-[#CCCCCC] mx-1" />
           <StaticLink
             href={item.href}
-            className="hover:text-[#C41E3A] transition-colors px-1.5 py-1 rounded"
+            className="hover:text-[#C41E3A] transition-colors"
           >
             {item.label}
           </StaticLink>