refactor: 에러코드 변경, email 제약조건 설정

Author: jaehyeon4406

src/main/java/com/devpath/domain/user/contorller/UserControllerDocs.java

@@ -36,7 +36,7 @@ ApiResponse<CursorResponseDto<CardPrevRes>> getCards(Long userId, Long cursor, I
         @Operation(summary = "명함 교환", description = "명함 코드를 입력하면 명함이 교환됩니다.")
         @ApiResponses({
                         @io.swagger.v3.oas.annotations.responses.ApiResponse(responseCode = "201", description = "명함 교환 성공"),
-                        @io.swagger.v3.oas.annotations.responses.ApiResponse(responseCode = "400", description = "FOLLOW_400: 이미 추가한 명함입니다"),
+                        @io.swagger.v3.oas.annotations.responses.ApiResponse(responseCode = "409", description = "FOLLOW_409: 이미 추가한 명함입니다"),
                         @io.swagger.v3.oas.annotations.responses.ApiResponse(responseCode = "404", description = "COMMON_404: 검색 결과가 없습니다.")
         })
         ResponseEntity<ApiResponse<Void>> exchangeCard(Long userId, Long cardCode);

src/main/java/com/devpath/domain/user/dto/UserProfileRequest.java

@@ -3,6 +3,7 @@
 import com.devpath.domain.user.enums.JobGroup;
 import com.devpath.domain.user.enums.Level;
 import com.devpath.domain.user.enums.TechStackName;
+import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.NotBlank;
 import jakarta.validation.constraints.NotNull;
 import jakarta.validation.constraints.Size;
@@ -25,6 +26,7 @@ public class UserProfileRequest {
     private String phone;
 
     @NotBlank(message = "이메일은 필수입니다")
+    @Email(message = "유효한 이메일 형식이 아닙니다")
     private String email;
 
     @NotBlank(message = "링크는 필수입니다")