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/js/pages/add-image.js

@@ -0,0 +1,76 @@
+window.goToFirstOrLastPage = goToFirstOrLastPage;
+
+document.getElementById('download-pdf').addEventListener('click', async () => {
+  const downloadButton = document.getElementById('download-pdf');
+  const originalContent = downloadButton.innerHTML;
+
+  downloadButton.disabled = true;
+  downloadButton.innerHTML = `
+    <span class="spinner-border spinner-border-sm" role="status" aria-hidden="true"></span>
+  `;
+
+  try {
+    const modifiedPdf = await DraggableUtils.getOverlayedPdfDocument();
+    const modifiedPdfBytes = await modifiedPdf.save();
+    const blob = new Blob([modifiedPdfBytes], { type: 'application/pdf' });
+    const link = document.createElement('a');
+    link.href = URL.createObjectURL(blob);
+    link.download = originalFileName + '_addedImage.pdf';
+    link.click();
+  } finally {
+    downloadButton.disabled = false;
+    downloadButton.innerHTML = originalContent;
+  }
+});
+let originalFileName = '';
+document.querySelector('input[name=pdf-upload]').addEventListener('change', async (event) => {
+  const fileInput = event.target;
+  fileInput.addEventListener('file-input-change', async (e) => {
+    const { allFiles } = e.detail;
+    if (allFiles && allFiles.length > 0) {
+      const file = allFiles[0];
+      originalFileName = file.name.replace(/\.[^/.]+$/, '');
+      const pdfData = await file.arrayBuffer();
+      pdfjsLib.GlobalWorkerOptions.workerSrc = './pdfjs-legacy/pdf.worker.mjs';
+      const pdfDoc = await pdfjsLib.getDocument({ data: pdfData }).promise;
+      await DraggableUtils.renderPage(pdfDoc, 0);
+
+      document.querySelectorAll('.show-on-file-selected').forEach((el) => {
+        el.style.cssText = '';
+      });
+    }
+  });
+});
+document.addEventListener('DOMContentLoaded', () => {
+  document.querySelectorAll('.show-on-file-selected').forEach((el) => {
+    el.style.cssText = 'display:none !important';
+  });
+  document.addEventListener('keydown', (e) => {
+    if (e.key === 'Delete') {
+      DraggableUtils.deleteDraggableCanvas(DraggableUtils.getLastInteracted());
+    }
+  });
+});
+
+const imageUpload = document.querySelector('input[name=image-upload]');
+imageUpload.addEventListener('change', (e) => {
+  if (!e.target.files) {
+    return;
+  }
+  for (const imageFile of e.target.files) {
+    var reader = new FileReader();
+    reader.readAsDataURL(imageFile);
+    reader.onloadend = function (e) {
+      DraggableUtils.createDraggableCanvasFromUrl(e.target.result);
+    };
+  }
+});
+
+async function goToFirstOrLastPage(page) {
+  if (page) {
+    const lastPage = DraggableUtils.pdfDoc.numPages;
+    await DraggableUtils.goToPage(lastPage - 1);
+  } else {
+    await DraggableUtils.goToPage(0);
+  }
+}