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/AdminPageHeader.tsx

@@ -0,0 +1,39 @@
+import type { LucideIcon } from "lucide-react";
+import type { ReactNode } from "react";
+
+/** 后台统一页头：36px 图标槽 + 标题 + 说明 + 可选右侧 CTA */
+export default function AdminPageHeader({
+  icon: Icon,
+  title,
+  description,
+  actions,
+}: {
+  icon: LucideIcon;
+  title: string;
+  description?: ReactNode;
+  actions?: ReactNode;
+}) {
+  return (
+    <div className="mb-5 flex items-start justify-between gap-3 flex-wrap">
+      <div className="min-w-0">
+        <h1
+          className="text-[22px] sm:text-[26px] font-extrabold tracking-tight flex items-center gap-2.5"
+          style={{ color: "var(--ink)" }}
+        >
+          <span
+            className="w-9 h-9 rounded-xl flex items-center justify-center shrink-0"
+            style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
+            aria-hidden
+          >
+            <Icon size={18} />
+          </span>
+          {title}
+        </h1>
+        {description != null && description !== "" && (
+          <p className="meta mt-1.5 text-[12.5px] leading-relaxed">{description}</p>
+        )}
+      </div>
+      {actions ? <div className="flex items-center gap-2 shrink-0 flex-wrap">{actions}</div> : null}
+    </div>
+  );
+}