Adjust YARP proxy to exclude specific API paths

Updated the middleware pipeline in `Program.cs` to use `app.MapWhen()` for conditional routing. The reverse proxy now excludes requests to `/swagger`, `/scalar`, and `/openapi` paths, ensuring these endpoints are handled separately. This change replaces the direct `app.MapReverseProxy()` call with a more selective approach, improving request handling for specific API paths.

EnvelopeGenerator.API/Program.cs

@@ -322,9 +322,19 @@ try
     app.UseAuthentication();
     app.UseAuthorization();
 
-    app.MapReverseProxy();
     app.MapControllers();
 
+    // Catch-all YARP proxy — only forward requests that are not swagger/scalar/openapi paths.
+    app.MapWhen(
+        ctx =>
+        {
+            var path = ctx.Request.Path.Value ?? string.Empty;
+            return !path.StartsWith("/swagger", StringComparison.OrdinalIgnoreCase) &&
+                   !path.StartsWith("/scalar", StringComparison.OrdinalIgnoreCase) &&
+                   !path.StartsWith("/openapi", StringComparison.OrdinalIgnoreCase);
+        },
+        branch => branch.UseRouting().UseEndpoints(e => e.MapReverseProxy()));
+
     app.Run();
 }
 catch (Exception ex)