V2 Validate PDF Signature tool (#4679)

# Description of Changes

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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 <77850077+Frooodle@users.noreply.github.com>

frontend/src/data/useTranslatedToolRegistry.tsx

@@ -108,6 +108,7 @@ import RemovePagesSettings from "../components/tools/removePages/RemovePagesSett
 import RemoveBlanksSettings from "../components/tools/removeBlanks/RemoveBlanksSettings";
 import AddPageNumbersAutomationSettings from "../components/tools/addPageNumbers/AddPageNumbersAutomationSettings";
 import OverlayPdfsSettings from "../components/tools/overlayPdfs/OverlayPdfsSettings";
+import ValidateSignature from "../tools/ValidateSignature";
 
 const showPlaceholderTools = true; // Show all tools; grey out unavailable ones in UI
 
@@ -281,10 +282,12 @@ export function useFlatToolRegistry(): ToolRegistry {
       validateSignature: {
         icon: <LocalIcon icon="verified-rounded" width="1.5rem" height="1.5rem" />,
         name: t("home.validateSignature.title", "Validate PDF Signature"),
-        component: null,
+        component: ValidateSignature,
         description: t("home.validateSignature.desc", "Verify digital signatures and certificates in PDF documents"),
         categoryId: ToolCategoryId.STANDARD_TOOLS,
         subcategoryId: SubcategoryId.VERIFICATION,
+        maxFiles: -1,
+        endpoints: ["validate-signature"],
         synonyms: getSynonyms(t, "validateSignature"),
         automationSettings: null
       },