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.Server/EnvelopeGenerator.Server.Client/Program.cs

@@ -6,6 +6,7 @@ using DevExpress.XtraReports.Web.Extensions;
 using DevExpress.DataAccess.Web;
 using DevExpress.XtraReports.Services;
 using System.Globalization;
+using EnvelopeGenerator.Application.Common.Configurations;
 
 var builder = WebAssemblyHostBuilder.CreateDefault(args);
 
@@ -31,6 +32,8 @@ builder.Services.AddScoped(sp => new HttpClient
 // Configuration Options
 builder.Services.Configure<PdfViewerOptions>(opts =>
     builder.Configuration.GetSection(PdfViewerOptions.SectionName).Bind(opts));
+builder.Services.Configure<SignatureFieldParams>(opts =>
+    builder.Configuration.GetSection(nameof(SignatureFieldParams)).Bind(opts));
 
 // Business Services
 builder.Services.AddScoped<DocumentService>();