Add global exception handling middleware

Introduced `ExceptionHandlingMiddleware` to handle exceptions
globally in the application. The middleware captures exceptions
thrown during the request pipeline, logs them, and returns
appropriate HTTP responses in JSON format.

Key features:
- Handles `JobException` with a 400 Bad Request response.
- Handles unhandled exceptions with a 500 Internal Server Error.
- Logs warnings for `JobException` and errors for unhandled
  exceptions.
- Sets response `ContentType` to `application/json` and writes
  error details as JSON.

Added necessary `using` directives for required namespaces.

ECMJobRunner.WebCron/Middleware/ExceptionHandlingMiddleware.cs

@@ -0,0 +1,74 @@
+using ECMJobRunner.Application.Common.Exceptions;
+using Microsoft.AspNetCore.Mvc;
+using System.Net;
+
+namespace ECMJobRunner.WebCron.Middleware;
+
+/// <summary>
+/// Middleware for handling exceptions globally in the application.
+/// Captures exceptions thrown during the request pipeline execution,
+/// logs them, and returns an appropriate HTTP response with a JSON error details.
+/// </summary>
+/// <remarks>
+/// Initializes a new instance of the <see cref="ExceptionHandlingMiddleware"/> class.
+/// </remarks>
+/// <param name="Next">The next middleware in the request pipeline.</param>
+/// <param name="Logger">The logger instance for logging exceptions.</param>
+public class ExceptionHandlingMiddleware(RequestDelegate Next, ILogger<ExceptionHandlingMiddleware> Logger)
+{
+    /// <summary>
+    /// Invokes the middleware to handle the HTTP request.
+    /// </summary>
+    /// <param name="context">The HTTP context of the current request.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    public async Task InvokeAsync(HttpContext context)
+    {
+        try
+        {
+            await Next(context); // Continue down the pipeline
+        }
+        catch (Exception ex)
+        {
+            await HandleExceptionAsync(context, ex, Logger);
+        }
+    }
+
+    /// <summary>
+    /// Handles exceptions by logging them and writing an appropriate JSON response.
+    /// </summary>
+    /// <param name="context">The HTTP context of the current request.</param>
+    /// <param name="exception">The exception that occurred.</param>
+    /// <param name="logger">The logger instance for logging the exception.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    private static async Task HandleExceptionAsync(HttpContext context, Exception exception, ILogger logger)
+    {
+        context.Response.ContentType = "application/json";
+
+        ValidationProblemDetails details;
+
+        switch (exception)
+        {
+            case JobException jobEx:
+                logger.LogWarning(jobEx, "Job exception occurred.");
+                context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
+                details = new()
+                {
+                    Title = "Job Exception",
+                    Detail = jobEx.Message
+                };
+                break;
+            default:
+                logger.LogError(exception, "Unhandled exception occurred.");
+                context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
+                details = new()
+                {
+                    Title = "Internal Server Error",
+                    Detail = "An unexpected error occurred. Please try again later."
+                };
+                break;
+        }
+
+        if (details is not null)
+            await context.Response.WriteAsJsonAsync(details);
+    }
+}