feat: API Key 재발급 API 구현 (#46)

- ApiKeyRefreshResponseDto 추가
- IServiceManagementService.RefreshApiKeyAsync 인터페이스 추가
- ServiceManagementService.RefreshApiKeyAsync 구현 (32~64자 랜덤 키 생성)
- ServiceController.RefreshApiKeyAsync 엔드포인트 추가

SPMS.API/Controllers/ServiceController.cs

@@ -63,4 +63,18 @@ public class ServiceController : ControllerBase
         var result = await _serviceManagementService.ChangeStatusAsync(serviceCode, request);
         return Ok(ApiResponse<ServiceResponseDto>.Success(result));
     }
+
+    [HttpPost("{serviceCode}/apikey/refresh")]
+    [SwaggerOperation(
+        Summary = "API Key 재발급",
+        Description = "서비스의 API Key를 재발급합니다. 기존 키는 즉시 무효화되며, 새 키는 1회만 표시됩니다.")]
+    [SwaggerResponse(200, "재발급 성공", typeof(ApiResponse<ApiKeyRefreshResponseDto>))]
+    [SwaggerResponse(401, "인증되지 않은 요청")]
+    [SwaggerResponse(403, "권한 없음")]
+    [SwaggerResponse(404, "서비스를 찾을 수 없음")]
+    public async Task<IActionResult> RefreshApiKeyAsync([FromRoute] string serviceCode)
+    {
+        var result = await _serviceManagementService.RefreshApiKeyAsync(serviceCode);
+        return Ok(ApiResponse<ApiKeyRefreshResponseDto>.Success(result));
+    }
 }

SPMS.Application/DTOs/Service/ApiKeyRefreshResponseDto.cs

@@ -0,0 +1,8 @@
+namespace SPMS.Application.DTOs.Service;
+
+public class ApiKeyRefreshResponseDto
+{
+    public string ServiceCode { get; set; } = string.Empty;
+    public string ApiKey { get; set; } = string.Empty;
+    public DateTime ApiKeyCreatedAt { get; set; }
+}

SPMS.Application/Interfaces/IServiceManagementService.cs

@@ -7,4 +7,5 @@ public interface IServiceManagementService
     Task<ServiceListResponseDto> GetListAsync(ServiceListRequestDto request);
     Task<ServiceResponseDto> GetByServiceCodeAsync(string serviceCode);
     Task<ServiceResponseDto> ChangeStatusAsync(string serviceCode, ChangeServiceStatusRequestDto request);
+    Task<ApiKeyRefreshResponseDto> RefreshApiKeyAsync(string serviceCode);
 }

SPMS.Application/Services/ServiceManagementService.cs

@@ -1,4 +1,5 @@
 using System.Linq.Expressions;
+using System.Security.Cryptography;
 using SPMS.Application.DTOs.Service;
 using SPMS.Application.Interfaces;
 using SPMS.Domain.Common;
@@ -110,6 +111,40 @@ public class ServiceManagementService : IServiceManagementService
         return MapToDto(service);
     }
 
+    public async Task<ApiKeyRefreshResponseDto> RefreshApiKeyAsync(string serviceCode)
+    {
+        var service = await _serviceRepository.GetByServiceCodeAsync(serviceCode);
+        if (service is null)
+        {
+            throw new SpmsException(
+                ErrorCodes.NotFound,
+                "서비스를 찾을 수 없습니다.",
+                404);
+        }
+
+        // 32~64자 랜덤 API Key 생성 (48자 = 36바이트 Base64)
+        var randomBytes = new byte[36];
+        using (var rng = RandomNumberGenerator.Create())
+        {
+            rng.GetBytes(randomBytes);
+        }
+        var newApiKey = Convert.ToBase64String(randomBytes);
+
+        service.ApiKey = newApiKey;
+        service.ApiKeyCreatedAt = DateTime.UtcNow;
+        service.UpdatedAt = DateTime.UtcNow;
+
+        _serviceRepository.Update(service);
+        await _unitOfWork.SaveChangesAsync();
+
+        return new ApiKeyRefreshResponseDto
+        {
+            ServiceCode = service.ServiceCode,
+            ApiKey = newApiKey,
+            ApiKeyCreatedAt = service.ApiKeyCreatedAt
+        };
+    }
+
     private static ServiceSummaryDto MapToSummaryDto(Service service)
     {
         return new ServiceSummaryDto