Multi module refactor (#3640)

# Description of Changes

Migrated Stirling PDF to a multi-module structure:

* Introduced new `:stirling-pdf` module
* Moved all the core logic and features of Stirling PDF into
`:stirling-pdf`
* Updated paths of jobs and scripts

---

## 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/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/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/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/DeveloperGuide.md#6-testing)
for more details.

stirling-pdf/src/main/resources/static/pdfjs-legacy/images/secondaryToolbarButton-spreadEven.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="none" viewBox="0 0 16 16"><path fill="#000" fill-rule="evenodd" d="M2 3.5C1.72421 3.5 1.5 3.72421 1.5 4V12.5C1.5 12.7758 1.72421 13 2 13H7.25V3.5H2ZM14 13H8.75V3.5H14C14.2758 3.5 14.5 3.72421 14.5 4V12.5C14.5 12.7758 14.2758 13 14 13ZM0 4C0 2.89579 0.895786 2 2 2H14C15.1042 2 16 2.89579 16 4V12.5C16 13.6042 15.1042 14.5 14 14.5H2C0.895786 14.5 0 13.6042 0 12.5V4ZM10 6.5H11.5V7.5H10V9H11.5V10H10V11.5H12.25C12.6642 11.5 13 11.1642 13 10.75V5.75C13 5.33579 12.6642 5 12.25 5H10V6.5ZM4.5 6.5H3V5H5.25C5.66421 5 6 5.33579 6 5.75V7.75C6 8.03408 5.8395 8.29378 5.58541 8.42082L4.5 8.96353V10H6V11.5H3.75C3.33579 11.5 3 11.1642 3 10.75V8.5C3 8.21592 3.1605 7.95622 3.41459 7.82918L4.5 7.28647V6.5Z"/></svg>