refactor: 로그인 확인 API에서의 불필요한 중복 DB 요청 제거

src/main/kotlin/roomescape/auth/web/AuthControllerV2.kt

@@ -33,9 +33,7 @@ class AuthControllerV2(
     override fun checkLogin(
         @CurrentUser user: CurrentUserContext,
     ): ResponseEntity<CommonApiResponse<CurrentUserContext>> {
-        val response = authService.checkLogin(user)
-
-        return ResponseEntity.ok(CommonApiResponse(response))
+        return ResponseEntity.ok(CommonApiResponse(user))
     }
 
     @PostMapping("/logout")