Refactor: Remove ProcessDocument and update roadmap

Removed the obsolete `ProcessDocument` folder and its files
(`ProcessDocumentCommand.cs`, `ProcessDocumentHandler.cs`,
`ProcessDocumentValidator.cs`) as part of Application Layer
cleanup. Updated `ROADMAP.md` to reflect progress, including
the start of `DevExpressPdfProcessor` implementation (Step 3.2)
and actionable steps for creating a test folder structure.
Documented the availability of the `DevExpress Universal License`.

DocumentOperator.Application/Features/Documents/ProcessDocument/ProcessDocumentCommand.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace DocumentOperator.Application.Features.Documents.ProcessDocument
-{
-    internal class ProcessDocumentCommand
-    {
-    }
-}

DocumentOperator.Application/Features/Documents/ProcessDocument/ProcessDocumentHandler.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace DocumentOperator.Application.Features.Documents.ProcessDocument
-{
-    internal class ProcessDocumentHandler
-    {
-    }
-}

DocumentOperator.Application/Features/Documents/ProcessDocument/ProcessDocumentValidator.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace DocumentOperator.Application.Features.Documents.ProcessDocument
-{
-    internal class ProcessDocumentValidator
-    {
-    }
-}