feat: 회원가입 API 구현 (#56)

- POST /v1/in/auth/signup 엔드포인트 추가 (AllowAnonymous)
- SignupRequestDto/SignupResponseDto 생성
- AuthService.SignupAsync 구현 (이메일 중복검사, AdminCode 생성, BCrypt 해싱)
- ApiResponse<T>.Success(data, msg) 오버로드 추가

SPMS.API/Controllers/AuthController.cs

@@ -19,6 +19,20 @@ public class AuthController : ControllerBase
         _authService = authService;
     }
 
+    [HttpPost("signup")]
+    [AllowAnonymous]
+    [SwaggerOperation(
+        Summary = "회원가입",
+        Description = "새로운 관리자 계정을 생성합니다. 이메일 인증이 필요합니다.")]
+    [SwaggerResponse(200, "회원가입 성공", typeof(ApiResponse<SignupResponseDto>))]
+    [SwaggerResponse(400, "잘못된 요청")]
+    [SwaggerResponse(409, "이미 사용 중인 이메일")]
+    public async Task<IActionResult> SignupAsync([FromBody] SignupRequestDto request)
+    {
+        var result = await _authService.SignupAsync(request);
+        return Ok(ApiResponse<SignupResponseDto>.Success(result, "회원가입 완료. 이메일 인증이 필요합니다."));
+    }
+
     [HttpPost("login")]
     [AllowAnonymous]
     [SwaggerOperation(

SPMS.Application/DTOs/Auth/SignupRequestDto.cs

@@ -0,0 +1,22 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace SPMS.Application.DTOs.Auth;
+
+public class SignupRequestDto
+{
+    [Required(ErrorMessage = "이메일은 필수입니다.")]
+    [EmailAddress(ErrorMessage = "올바른 이메일 형식이 아닙니다.")]
+    public string Email { get; set; } = string.Empty;
+
+    [Required(ErrorMessage = "비밀번호는 필수입니다.")]
+    [MinLength(8, ErrorMessage = "비밀번호는 8자 이상이어야 합니다.")]
+    public string Password { get; set; } = string.Empty;
+
+    [Required(ErrorMessage = "이름은 필수입니다.")]
+    [StringLength(50, ErrorMessage = "이름은 50자 이내여야 합니다.")]
+    public string Name { get; set; } = string.Empty;
+
+    [Required(ErrorMessage = "전화번호는 필수입니다.")]
+    [StringLength(20, ErrorMessage = "전화번호는 20자 이내여야 합니다.")]
+    public string Phone { get; set; } = string.Empty;
+}

SPMS.Application/DTOs/Auth/SignupResponseDto.cs

@@ -0,0 +1,12 @@
+using System.Text.Json.Serialization;
+
+namespace SPMS.Application.DTOs.Auth;
+
+public class SignupResponseDto
+{
+    [JsonPropertyName("admin_code")]
+    public string AdminCode { get; set; } = string.Empty;
+
+    [JsonPropertyName("email")]
+    public string Email { get; set; } = string.Empty;
+}

SPMS.Application/Interfaces/IAuthService.cs

@@ -4,6 +4,7 @@ namespace SPMS.Application.Interfaces;
 
 public interface IAuthService
 {
+    Task<SignupResponseDto> SignupAsync(SignupRequestDto request);
     Task<LoginResponseDto> LoginAsync(LoginRequestDto request);
     Task<TokenRefreshResponseDto> RefreshTokenAsync(TokenRefreshRequestDto request);
     Task LogoutAsync(long adminId);

SPMS.Application/Services/AuthService.cs

@@ -3,6 +3,8 @@ using SPMS.Application.DTOs.Auth;
 using SPMS.Application.Interfaces;
 using SPMS.Application.Settings;
 using SPMS.Domain.Common;
+using SPMS.Domain.Entities;
+using SPMS.Domain.Enums;
 using SPMS.Domain.Exceptions;
 using SPMS.Domain.Interfaces;
 
@@ -27,6 +29,46 @@ public class AuthService : IAuthService
         _jwtSettings = jwtSettings.Value;
     }
 
+    public async Task<SignupResponseDto> SignupAsync(SignupRequestDto request)
+    {
+        // 1. 이메일 중복 검사
+        if (await _adminRepository.EmailExistsAsync(request.Email))
+        {
+            throw new SpmsException(
+                ErrorCodes.Conflict,
+                "이미 사용 중인 이메일입니다.",
+                409);
+        }
+
+        // 2. AdminCode 생성 (UUID 12자)
+        var adminCode = Guid.NewGuid().ToString("N")[..12].ToUpper();
+
+        // 3. Admin 엔티티 생성
+        var admin = new Admin
+        {
+            AdminCode = adminCode,
+            Email = request.Email,
+            Password = BCrypt.Net.BCrypt.HashPassword(request.Password),
+            Name = request.Name,
+            Phone = request.Phone,
+            Role = AdminRole.User,
+            EmailVerified = false,
+            CreatedAt = DateTime.UtcNow,
+            IsDeleted = false
+        };
+
+        // 4. 저장
+        await _adminRepository.AddAsync(admin);
+        await _unitOfWork.SaveChangesAsync();
+
+        // 5. 응답 반환
+        return new SignupResponseDto
+        {
+            AdminCode = admin.AdminCode,
+            Email = admin.Email
+        };
+    }
+
     public async Task<LoginResponseDto> LoginAsync(LoginRequestDto request)
     {
         // 1. 이메일로 관리자 조회

SPMS.Domain/Common/ApiResponse.cs

@@ -28,6 +28,9 @@ public class ApiResponse<T> : ApiResponse
     public static ApiResponse<T> Success(T data)
         => new() { Result = true, Code = ErrorCodes.Success, Data = data };
 
+    public static ApiResponse<T> Success(T data, string msg)
+        => new() { Result = true, Code = ErrorCodes.Success, Data = data, Msg = msg };
+
     public new static ApiResponse<T> Fail(string code, string msg)
         => new() { Result = false, Code = code, Msg = msg };
 }