fix: 表格单元格缺少内边距，内容紧贴左边框

Tailwind 的 @tailwindcss/typography 插件默认不给 th/td 设置 padding，
加上 prose-th:px-3 prose-th:py-2 / prose-td:px-3 prose-td:py-2 解决。

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

pages/posts/[slug].vue

@@ -123,8 +123,8 @@ function formatDate(date: string) {
                 prose-code:bg-muted prose-code:text-foreground prose-code:rounded prose-code:px-1.5 prose-code:py-0.5 prose-code:before:content-none prose-code:after:content-none
                 prose-pre:bg-muted prose-pre:px-4 prose-pre:py-2 prose-pre:text-foreground prose-pre:overflow-x-auto
                 prose-hr:border-border
-                prose-th:border prose-th:border-border prose-th:bg-muted
-                prose-td:border prose-td:border-border
+                prose-th:border prose-th:border-border prose-th:bg-muted prose-th:px-3 prose-th:py-2
+                prose-td:border prose-td:border-border prose-td:px-3 prose-td:py-2
                 prose-img:rounded-lg
                 anim-fade-in-up anim-delay-1">
       <ContentRenderer :value="post" />