polish(admin): 抽出后台控件包并统一各页布局与交互

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/components/admin/AdminEmpty.tsx

@@ -0,0 +1,30 @@
+import type { ReactNode } from "react";
+
+/** 图标 + 主文案 + 辅文案 */
+export default function AdminEmpty({
+  icon,
+  title,
+  description,
+  className = "",
+}: {
+  icon: ReactNode;
+  title: string;
+  description?: string;
+  className?: string;
+}) {
+  return (
+    <div className={`text-center py-16 px-6 ${className}`.trim()}>
+      <span
+        className="inline-flex w-12 h-12 rounded-full items-center justify-center mb-3"
+        style={{ background: "var(--panel-2)", color: "var(--ink-3)" }}
+        aria-hidden
+      >
+        {icon}
+      </span>
+      <p className="text-[14.5px]" style={{ color: "var(--ink)" }}>
+        {title}
+      </p>
+      {description ? <p className="meta mt-1.5 text-[12.5px]">{description}</p> : null}
+    </div>
+  );
+}