feat(i18n, agents, players): enhance localization and improve agent and player management interfaces

Updated localization files for English and Nepali, adding new entries and refining existing translations for better clarity. Enhanced the agent management interface with improved delegation features and child agent creation prompts. Improved player management functionalities, including confirmation dialogs for player actions and better handling of player creation and editing processes.

src/app/error.tsx

@@ -0,0 +1,42 @@
+"use client";
+
+import { useEffect } from "react";
+import Link from "next/link";
+
+export default function AdminError({
+  error,
+  reset,
+}: {
+  error: Error & { digest?: string };
+  reset: () => void;
+}): React.ReactElement {
+  useEffect(() => {
+    console.error("[AdminError]", error);
+  }, [error]);
+
+  return (
+    <div className="flex min-h-[60vh] flex-col items-center justify-center gap-4 p-6 text-center">
+      <h1 className="text-xl font-semibold">页面加载失败</h1>
+      <p className="max-w-md text-sm text-muted-foreground">
+        管理后台遇到意外错误，请重试或返回首页。
+      </p>
+      {process.env.NODE_ENV === "development" ? (
+        <pre className="max-w-xl overflow-auto rounded-md bg-muted p-3 text-left text-xs">
+          {error.message}
+        </pre>
+      ) : null}
+      <div className="flex gap-3">
+        <button
+          type="button"
+          onClick={reset}
+          className="rounded-md border px-4 py-2 text-sm"
+        >
+          重试
+        </button>
+        <Link href="/admin" className="rounded-md bg-primary px-4 py-2 text-sm text-primary-foreground">
+          返回首页
+        </Link>
+      </div>
+    </div>
+  );
+}

src/app/not-found.tsx

@@ -0,0 +1,13 @@
+import Link from "next/link";
+
+export default function AdminNotFound(): React.ReactElement {
+  return (
+    <div className="flex min-h-[60vh] flex-col items-center justify-center gap-4 p-6 text-center">
+      <h1 className="text-xl font-semibold">页面不存在</h1>
+      <p className="text-sm text-muted-foreground">请检查地址或返回管理后台首页。</p>
+      <Link href="/admin" className="rounded-md bg-primary px-4 py-2 text-sm text-primary-foreground">
+        返回首页
+      </Link>
+    </div>
+  );
+}