refactor: 닉네임 길이제한 2~20자.

Author: sapiens2000

src/main/java/com/example/log4u/domain/user/dto/UserProfileMakeRequestDto.java

@@ -1,9 +1,12 @@
 package com.example.log4u.domain.user.dto;
 
 import jakarta.validation.constraints.NotEmpty;
+import jakarta.validation.constraints.Size;
 
 public record UserProfileMakeRequestDto(
-	@NotEmpty String nickname,
+	@NotEmpty
+	@Size(min = 2, max = 20, message = "닉네임은 2자 이상 20자 이하로 입력해주세요.")
+	String nickname,
 	String statusMessage,
 	String profileImage
 ) {