Added database entities, started with node crud

MoonlightServers.ApiServer/Database/Entities/Backup.cs

@@ -0,0 +1,18 @@
+using MoonlightServers.Shared.Enums;
+
+namespace MoonlightServers.ApiServer.Database.Entities;
+
+public class Backup
+{
+    public int Id { get; set; }
+
+    public string Name { get; set; }
+    public BackupState State { get; set; }
+
+    public long Size { get; set; }
+
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+    public DateTime FinishedAt { get; set; } = DateTime.UtcNow;
+
+    public Server Server { get; set; }
+}