refactor: Remove metadata export from sign-in page

src/app/(auth)/sign-in/metadata.ts

@@ -0,0 +1,6 @@
+import { Metadata } from "next";
+
+export const metadata: Metadata = {
+  title: "Login",
+  description: "Login to your account",
+};

src/app/(auth)/sign-in/page.tsx

@@ -1,7 +1,6 @@
 "use client";
 
 import { useEffect } from "react";
-import { Metadata } from "next";
 import Link from "next/link";
 import { ChevronLeft, MessageCircleCode } from "lucide-react";
 
@@ -13,11 +12,6 @@ interface Props {
   searchParams: { state?: string };
 }
 
-export const metadata: Metadata = {
-  title: "Login",
-  description: "Login to your account",
-};
-
 export default function LoginPage({ searchParams }: Props) {
   useEffect(() => {
     // 如果有 state 参数，保存到 cookie