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/file-utils.js

@@ -0,0 +1,31 @@
+class FileUtils {
+  static extractFileExtension(filename) {
+    if (!filename || filename.trim().length <= 0) return "";
+    let trimmedName = filename.trim();
+    return trimmedName.substring(trimmedName.lastIndexOf(".") + 1);
+  }
+
+  static transformFileSize(size) {
+    if (!size) return `0Bs`;
+    let oneKB = 1024;
+    let oneMB = oneKB * 1024;
+    let oneGB = oneMB * 1024;
+    let oneTB = oneGB * 1024;
+
+    if (size < oneKB) return `${this._toFixed(size)}Bs`;
+    else if (oneKB <= size && size < oneMB) return `${this._toFixed(size / oneKB)}KBs`;
+    else if (oneMB <= size && size < oneGB) return `${this._toFixed(size / oneMB)}MBs`;
+    else if (oneGB <= size && size < oneTB) return `${this._toFixed(size / oneGB)}GBs`;
+    else return `${this._toFixed(size / oneTB)}TBs`;
+  }
+
+  static _toFixed(val, digits = 1) {
+    // Return value without ending 0s after decimal point
+    // Example: if res == 145.0 then return 145, else if 145.x (where x != 0) return 145.x
+    let res = val.toFixed(digits);
+    let resRounded = (res|0);
+    return res == resRounded ? resRounded : res;
+  }
+}
+
+export default FileUtils;