Add configurable SignatureFieldParams class

Introduce `SignatureFieldParams` class to manage signature field dimensions with configurable `Width` and `Height`. Integrate this configuration into the service collection and replace hardcoded dimensions in `CreateEnvelopeCommandHandler.cs` and `SenderEditorPage.razor`. Update `appsettings.json` to include the new configuration section, allowing runtime adjustments.

EnvelopeGenerator.Application/Envelopes/Commands/CreateEnvelopeCommandHandler.cs

@@ -47,6 +47,8 @@ public class CreateEnvelopeCommandHandler : IRequestHandler<CreateEnvelopeComman
 
     private DispatcherParams DispatcherParams => _provider.GetRequiredService<IOptions<DispatcherParams>>().Value;
 
+    private SignatureFieldParams SignatureFieldParams => _provider.GetRequiredService<IOptionsMonitor<SignatureFieldParams>>().CurrentValue;
+
     private IConfigService ConfigService => _provider.GetRequiredService<IConfigService>();
 
     private IMediator Mediator => _provider.GetRequiredService<IMediator>();
@@ -444,8 +446,8 @@ public class CreateEnvelopeCommandHandler : IRequestHandler<CreateEnvelopeComman
                     ElementType = 1,
                     X = field.X,
                     Y = field.Y,
-                    Width = 1.77,
-                    Height = 1.96,
+                    Width = SignatureFieldParams.Width,
+                    Height = SignatureFieldParams.Height,
                     Page = field.Page,
                     Required = true,
                     ReadOnly = false,