feat: redirect www.essentialcsharp.com to apex domain

Adds a 301 redirect in the production middleware pipeline that strips
the 'www.' prefix and redirects to the apex domain. Runs after
UseForwardedHeaders so the real Host header is available behind the
Azure Container Apps ingress proxy.

Author: BenjaminMichaelis

EssentialCSharp.Web/Program.cs

@@ -515,6 +515,20 @@ await McpJsonRpcResponseWriter.WriteErrorAsync(
             app.UseSecurityHeadersMiddleware(new SecurityHeadersBuilder()
                 .AddDefaultSecurePolicy()
                 .AddContentSecurityPolicy(csp));
+
+            // Redirect www.essentialcsharp.com → essentialcsharp.com (permanent 301)
+            // Must be after UseForwardedHeaders so the Host header reflects the real hostname.
+            app.Use(async (context, next) =>
+            {
+                if (context.Request.Host.Host.StartsWith("www.", StringComparison.OrdinalIgnoreCase))
+                {
+                    string apexHost = context.Request.Host.Host[4..];
+                    string redirectUrl = $"{context.Request.Scheme}://{apexHost}{context.Request.PathBase}{context.Request.Path}{context.Request.QueryString}";
+                    context.Response.Redirect(redirectUrl, permanent: true);
+                    return;
+                }
+                await next(context);
+            });
         }
         else
         {