feat: 이메일 중복 체크 API 구현 (#58)

POST /v1/in/auth/email/check 엔드포인트 추가.
기존 EmailExistsAsync 활용하여 이메일 사용 가능 여부 반환.

SPMS.API/Controllers/AuthController.cs

@@ -33,6 +33,19 @@ public class AuthController : ControllerBase
         return Ok(ApiResponse<SignupResponseDto>.Success(result, "회원가입 완료. 이메일 인증이 필요합니다."));
     }
 
+    [HttpPost("email/check")]
+    [AllowAnonymous]
+    [SwaggerOperation(
+        Summary = "이메일 중복 체크",
+        Description = "회원가입 전 이메일 사용 가능 여부를 확인합니다.")]
+    [SwaggerResponse(200, "이메일 중복 체크 성공", typeof(ApiResponse<EmailCheckResponseDto>))]
+    [SwaggerResponse(400, "잘못된 요청")]
+    public async Task<IActionResult> CheckEmailAsync([FromBody] EmailCheckRequestDto request)
+    {
+        var result = await _authService.CheckEmailAsync(request);
+        return Ok(ApiResponse<EmailCheckResponseDto>.Success(result));
+    }
+
     [HttpPost("login")]
     [AllowAnonymous]
     [SwaggerOperation(

SPMS.Application/DTOs/Auth/EmailCheckRequestDto.cs

@@ -0,0 +1,10 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace SPMS.Application.DTOs.Auth;
+
+public class EmailCheckRequestDto
+{
+    [Required(ErrorMessage = "이메일은 필수입니다.")]
+    [EmailAddress(ErrorMessage = "올바른 이메일 형식이 아닙니다.")]
+    public string Email { get; set; } = string.Empty;
+}

SPMS.Application/DTOs/Auth/EmailCheckResponseDto.cs

@@ -0,0 +1,11 @@
+using System.Text.Json.Serialization;
+
+namespace SPMS.Application.DTOs.Auth;
+
+public class EmailCheckResponseDto
+{
+    public string Email { get; set; } = string.Empty;
+
+    [JsonPropertyName("is_available")]
+    public bool IsAvailable { get; set; }
+}

SPMS.Application/Interfaces/IAuthService.cs

@@ -9,4 +9,5 @@ public interface IAuthService
     Task<TokenRefreshResponseDto> RefreshTokenAsync(TokenRefreshRequestDto request);
     Task LogoutAsync(long adminId);
     Task ChangePasswordAsync(long adminId, ChangePasswordRequestDto request);
+    Task<EmailCheckResponseDto> CheckEmailAsync(EmailCheckRequestDto request);
 }

SPMS.Application/Services/AuthService.cs

@@ -215,4 +215,14 @@ public class AuthService : IAuthService
         _adminRepository.Update(admin);
         await _unitOfWork.SaveChangesAsync();
     }
+
+    public async Task<EmailCheckResponseDto> CheckEmailAsync(EmailCheckRequestDto request)
+    {
+        var exists = await _adminRepository.EmailExistsAsync(request.Email);
+        return new EmailCheckResponseDto
+        {
+            Email = request.Email,
+            IsAvailable = !exists
+        };
+    }
 }