Add OpenTelemetry error span handling infrastructure

Introduce infrastructure for handling error spans with OpenTelemetry, including `DefaultErrorSpanHandler` and `FaultExceptionErrorSpanHandler`. Define core abstractions (`ErrorSpanHandlerBase`, `IErrorSpanHandler`) and utilities for customizing OpenTelemetry integration. This enables improved error tracing and categorization in workflows.

src/modules/Elsa.OpenTelemetry/Abstractions/ErrorSpanHandlerBase.cs

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+using Elsa.OpenTelemetry.Contracts;
+using Elsa.OpenTelemetry.Models;
+
+namespace Elsa.OpenTelemetry.Abstractions;
+
+public abstract class ErrorSpanHandlerBase : IErrorSpanHandler
+{
+    public abstract void Handle(ErrorSpanContext context);
+}

src/modules/Elsa.OpenTelemetry/Contracts/IErrorSpanHandler.cs

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+using Elsa.OpenTelemetry.Abstractions;
+using Elsa.OpenTelemetry.Models;
+
+namespace Elsa.OpenTelemetry.Contracts;
+
+public interface IErrorSpanHandler
+{
+    void Handle(ErrorSpanContext context);
+}
+

src/modules/Elsa.OpenTelemetry/Extensions/ModuleExtensions.cs

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+using Elsa.Features.Services;
+using Elsa.OpenTelemetry.Features;
+
+// ReSharper disable once CheckNamespace
+namespace Elsa.Extensions;
+
+public static class ModuleExtensions
+{
+    public static IModule UseOpenTelemetry(this IModule configuration, Action<OpenTelemetryFeature>? configure = null)
+    {
+        configuration.Configure(configure);
+        return configuration;
+    }
+}

src/modules/Elsa.OpenTelemetry/Handlers/DefaultErrorSpanHandler.cs

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+using Elsa.OpenTelemetry.Abstractions;
+using Elsa.OpenTelemetry.Models;
+
+namespace Elsa.OpenTelemetry.Handlers;
+
+public class DefaultErrorSpanHandler : ErrorSpanHandlerBase
+{
+    public override void Handle(ErrorSpanContext context)
+    {
+        var span = context.Span;
+        var exception = context.Exception;
+        var errorMessage = string.IsNullOrWhiteSpace(exception?.Message) ? "Unknown error" : exception.Message;
+        span.SetTag("error", true);
+        span.SetTag("error.message", errorMessage);
+
+        if (exception != null)
+        {
+            span.SetTag("error.exceptionType", exception.GetType().FullName);
+
+            if (!string.IsNullOrEmpty(exception.StackTrace))
+                span.SetTag("error.stackTrace", exception.StackTrace);
+        }
+    }
+}

src/modules/Elsa.OpenTelemetry/Handlers/FaultExceptionErrorSpanHandler.cs

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+using Elsa.OpenTelemetry.Abstractions;
+using Elsa.OpenTelemetry.Models;
+using Elsa.Workflows.Exceptions;
+
+namespace Elsa.OpenTelemetry.Handlers;
+
+public class FaultExceptionErrorSpanHandler : ErrorSpanHandlerBase
+{
+    public override void Handle(ErrorSpanContext context)
+    {
+        if(context.Exception is not FaultException faultException)
+            return;
+        
+        var span = context.Span;
+        span.SetTag("error.code", faultException.Code);
+        span.SetTag("error.category", faultException.Category);
+        span.SetTag("error.faultType", faultException.Type);
+    }
+}

src/modules/Elsa.OpenTelemetry/Models/ErrorSpanContext.cs

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+using System.Diagnostics;
+
+namespace Elsa.OpenTelemetry.Models;
+
+public class ErrorSpanContext(Activity span, Exception? exception)
+{
+    public Activity Span => span;
+    public Exception? Exception => exception;
+}