feat: added DI to Client

JOBot.TClient/Core/Services/UserService.cs

@@ -0,0 +1,18 @@
+using User = JOBot.Proto.User;
+
+namespace JOBot.TClient.Core.Services;
+
+public class UserService(User.UserClient client)
+{
+    public async Task<bool> RegisterAsync(long userId, string? username)
+    {
+        
+        var response = await client.RegisterAsync(new()
+        {
+            UserId = userId, 
+            Username = username
+        });
+
+        return response.Success;
+    }
+}