Fix: 회원가입 인증 리다이렉트 처리와 UI 그라디언트 클래스 수정

app/auth/callback/route.ts
- 이메일 인증 완료 판별을 세션 생성 시간 기준에서 쿼리 파라미터(auth_type=signup) 기반으로 변경
- 회원가입 인증인 경우 자동 로그인 세션 종료 후 로그인 페이지로 리다이렉트 처리

features/auth/actions.ts
- 회원가입 시 이메일 리다이렉트 URL에 auth_type=signup 쿼리 파라미터 추가

app/forgot-password/page.tsx
- 배경 및 카드 아이콘의 Tailwind 클래스명 일부 수정(bg-gradient-to→bg-linear-to, radial-gradient var() 구문 정리)

app/login/page.tsx
- 배경 및 카드 아이콘의 Tailwind 클래스명 일부 정리 및 일관화

app/reset-password/page.tsx
- 배경 및 카드 아이콘의 Tailwind 클래스명 일부 정리 및 일관화

app/signup/page.tsx
- 배경 및 카드 아이콘의 Tailwind 클래스명 일부 정리 및 일관화

features/auth/components/reset-password-form.tsx
- 버튼 그라디언트 클래스명(bg-gradient-to-r→bg-linear-to-r) 수정

app/forgot-password/page.tsx

@@ -27,9 +27,9 @@ export default async function ForgotPasswordPage({
   const { message } = await searchParams;
 
   return (
-    <div className="relative flex min-h-screen items-center justify-center overflow-hidden bg-gradient-to-br from-gray-50 via-white to-gray-100 px-4 py-12 dark:from-black dark:via-gray-950 dark:to-gray-900">
-      <div className="absolute inset-0 bg-[radial-gradient(ellipse_at_top_right,_var(--tw-gradient-stops))] from-gray-200/30 via-gray-100/15 to-transparent dark:from-gray-800/30 dark:via-gray-900/20" />
-      <div className="absolute inset-0 bg-[radial-gradient(ellipse_at_bottom_left,_var(--tw-gradient-stops))] from-gray-300/30 via-gray-200/15 to-transparent dark:from-gray-700/30 dark:via-gray-800/20" />
+    <div className="relative flex min-h-screen items-center justify-center overflow-hidden bg-linear-to-br from-gray-50 via-white to-gray-100 px-4 py-12 dark:from-black dark:via-gray-950 dark:to-gray-900">
+      <div className="absolute inset-0 bg-[radial-gradient(ellipse_at_top_right,var(--tw-gradient-stops))] from-gray-200/30 via-gray-100/15 to-transparent dark:from-gray-800/30 dark:via-gray-900/20" />
+      <div className="absolute inset-0 bg-[radial-gradient(ellipse_at_bottom_left,var(--tw-gradient-stops))] from-gray-300/30 via-gray-200/15 to-transparent dark:from-gray-700/30 dark:via-gray-800/20" />
 
       <div className="absolute left-1/4 top-1/4 h-64 w-64 animate-pulse rounded-full bg-gray-300/20 blur-3xl dark:bg-gray-700/20" />
       <div className="absolute bottom-1/4 right-1/4 h-64 w-64 animate-pulse rounded-full bg-gray-400/20 blur-3xl delay-700 dark:bg-gray-600/20" />
@@ -39,7 +39,7 @@ export default async function ForgotPasswordPage({
 
         <Card className="border-white/20 bg-white/70 shadow-2xl backdrop-blur-xl dark:border-white/10 dark:bg-gray-900/70">
           <CardHeader className="space-y-3 text-center">
-            <div className="mx-auto mb-2 flex h-16 w-16 items-center justify-center rounded-2xl bg-gradient-to-br from-gray-800 to-black shadow-lg dark:from-white dark:to-gray-200">
+            <div className="mx-auto mb-2 flex h-16 w-16 items-center justify-center rounded-2xl bg-linear-to-br from-gray-800 to-black shadow-lg dark:from-white dark:to-gray-200">
               <span className="text-sm font-semibold">MAIL</span>
             </div>
             <CardTitle className="text-3xl font-bold tracking-tight">
@@ -72,7 +72,7 @@ export default async function ForgotPasswordPage({
 
               <Button
                 formAction={requestPasswordReset}
-                className="h-11 w-full bg-gradient-to-r from-gray-900 to-black font-semibold text-white shadow-lg transition-all hover:from-black hover:to-gray-800 hover:shadow-xl dark:from-white dark:to-gray-100 dark:text-black dark:hover:from-gray-100 dark:hover:to-white"
+                className="h-11 w-full bg-linear-to-r from-gray-900 to-black font-semibold text-white shadow-lg transition-all hover:from-black hover:to-gray-800 hover:shadow-xl dark:from-white dark:to-gray-100 dark:text-black dark:hover:from-gray-100 dark:hover:to-white"
               >
                 재설정 링크 보내기
               </Button>