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.

testing/test.sh

@@ -23,7 +23,7 @@ check_health() {
     local end=$((SECONDS+60))
 
     echo -n "Waiting for $service_name to become healthy..."
-    until [ "$(docker inspect --format='{{json .State.Health.Status}}' "$service_name")" == '"healthy"' ] || [ $SECONDS -ge $end ]; do
+    until [ "$(docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{else}}healthy{{end}}' "$service_name")" == "healthy" ] || [ $SECONDS -ge $end ]; do
         sleep 3
         echo -n "."
         if [ $SECONDS -ge $end ]; then