refactor: migrate img tags to next/image and fix hook usage

src/app/auth/components/auth-email-panel.tsx

@@ -13,6 +13,7 @@
  *   - Spacer + AuthLegalText
  *   - 顶部 "← Back" 按钮由父级 AuthPanel 渲染（悬浮 40×40 圆形）
  */
+import Image from "next/image";
 import { useState } from "react";
 
 import { useAuthState } from "@/stores/auth/auth-context";
@@ -48,10 +49,13 @@ export function AuthEmailPanel({
         {mode === "login" ? (
           <>
             <div className={styles.spacer24} />
-            <img
+            <Image
               src="/images/auth/ic-logo-login.png"
               alt="Cozsweet"
+              width={120}
+              height={120}
               className={styles.logo}
+              priority
             />
           </>
         ) : (