PdfContainer: zero-pad numeric suffix in nameAndArchiveFiles (#4265)

# Description of Changes

Zero pad the numeric suffix in `PdfContainer.nameAndArchiveFiles` to
close #4263.

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] 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)
- [x] I have performed a self-review of my own code
- [x] 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>

app/core/src/main/resources/static/js/multitool/PdfContainer.js

@@ -694,7 +694,7 @@ class PdfContainer {
       const documentBlob = new Blob([pdfBytesArray[i]], {
         type: 'application/pdf',
       });
-      zip.file(baseNameString + '-' + (i + 1) + '.pdf', documentBlob);
+      zip.file(baseNameString + '-' + String(i + 1).padStart(1 + Math.floor(Math.log10(pdfBytesArray.length)), "0") + '.pdf', documentBlob);
     }
 
     return zip;