Added user add modal and converted to dark mode

HopFrame.Web/Model/RegisterData.cs

@@ -4,4 +4,8 @@ namespace HopFrame.Web.Model;
 
 public class RegisterData : UserRegister {
     public string RepeatedPassword { get; set; }
+
+    public bool PasswordsMatch => Password == RepeatedPassword;
+    public bool PasswordIsValid => Password.Length >= 8;
+    public bool EmailIsValid => Email.Contains('@') && Email.Contains('.') && !Email.EndsWith('.');
 }

HopFrame.Web/Model/UserAdd.cs

@@ -0,0 +1,5 @@
+namespace HopFrame.Web.Model;
+
+public class UserAdd : RegisterData {
+    public string Group { get; set; }
+}