V2 Validate PDF Signature tool (#4679)

# Description of Changes

<!--
Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: Anthony Stirling <[email protected]>

frontend/src/components/layout/Workbench.tsx

@@ -5,6 +5,7 @@ import { useToolWorkflow } from '../../contexts/ToolWorkflowContext';
 import { useFileHandler } from '../../hooks/useFileHandler';
 import { useFileState } from '../../contexts/FileContext';
 import { useNavigationState, useNavigationActions } from '../../contexts/NavigationContext';
+import { isBaseWorkbench } from '../../types/workbench';
 import { useViewer } from '../../contexts/ViewerContext';
 import './Workbench.css';
 
@@ -33,7 +34,8 @@ export default function Workbench() {
     sidebarsVisible,
     setPreviewFile,
     setPageEditorFunctions,
-    setSidebarsVisible
+    setSidebarsVisible,
+    customWorkbenchViews,
   } = useToolWorkflow();
 
   const { handleToolSelect } = useToolWorkflow();
@@ -137,9 +139,14 @@ export default function Workbench() {
         );
 
       default:
-        return (
-          <LandingPage/>
-        );
+        if (!isBaseWorkbench(currentView)) {
+          const customView = customWorkbenchViews.find((view) => view.workbenchId === currentView && view.data != null);
+          if (customView) {
+            const CustomComponent = customView.component;
+            return <CustomComponent data={customView.data} />;
+          }
+        }
+        return <LandingPage />;
     }
   };
 
@@ -157,6 +164,7 @@ export default function Workbench() {
         <TopControls
           currentView={currentView}
           setCurrentView={setCurrentView}
+          customViews={customWorkbenchViews}
           activeFiles={activeFiles.map(f => {
             const stub = selectors.getStirlingFileStub(f.fileId);
             return { fileId: f.fileId, name: f.name, versionNumber: stub?.versionNumber };