Added database entities, started with node crud

MoonlightServers.ApiServer/Database/Entities/Network.cs

@@ -0,0 +1,11 @@
+namespace MoonlightServers.ApiServer.Database.Entities;
+
+public class Network
+{
+    public int Id { get; set; }
+
+    public string Name { get; set; }
+
+    public Node Node { get; set; }
+    public List<Server> Servers { get; set; } = new();
+}