Merge pull request 'database anpassung' (#40) from enhancement/database-update into staging

Reviewed-on: #40

Watcher/Controllers/MonitoringController.cs

@@ -244,6 +244,14 @@ public class MonitoringController : Controller
             return BadRequest(new { error = "Invalid Payload", details = errors });
         }
 
+        // Prüfen, ob der Server existiert
+        var serverExists = await _context.Servers.AnyAsync(s => s.Id == dto.Server_id);
+        if (!serverExists)
+        {
+            _logger.LogError($"Server with ID {dto.Server_id} does not exist.");
+            return BadRequest(new { error = "Server not found", details = $"Server with ID {dto.Server_id} does not exist. Please register the server first." });
+        }
+
         List<Container> newContainers =
             JsonSerializer.Deserialize<List<Container>>(dto.Containers.GetRawText())
             ?? new List<Container>();