Upload File Size Limit (#3334)

# Description of Changes

The change this PR aims to introduce is a setting for enabling an upload
file size limit. The author of the issue mentioned in this PR wanted
this feature as they themselves enforced a limit of 50MB file sizes on
their NGINX configuration.
This was implemented by adding an entry to the
[settings.yml.template](e52fc0e478/src/main/resources/settings.yml.template)
file. This entry has two sub-configurations in which you declare if the
application should enable upload file size limiting and then you declare
the limit itself.

For this to be available in code, a new field in the
[System](e52fc0e478/src/main/java/stirling/software/SPDF/model/ApplicationProperties.java (L280))
class was added, one named `uploadLimit`.

After that, inside the [AppConfig](url) class, a new thymeleaf bean was
created, one called `uploadLimit`. This bean takes the values available
in the `System` class and creates a `long` value representing the limit
value. This value is interpreted as non-existent if it is `0`, otherwise
it is the value in `bytes` of the upload limit.

In order to make this value available in the
[common.html](e52fc0e478/src/main/resources/templates/fragments/common.html)
file, where the submitFile form is imported from, a new controller
[GlobalUploadLimitWebController](e52fc0e478/src/main/java/stirling/software/SPDF/controller/web/GlobalUploadLimitWebController.java)
was created. This controller has the tag `ControllerAdvice` so that
every controller has the `ModelAttributes` defined within it. I am not
sure if this was a good approach but upon first investigations, I
couldn't find another method to make these attributes available in every
Controller, or template. If there is already a place like this in the
code with this specific purpose, please let me know so I can fix it.

After making these attributes available, I updated the code in
`common.html`to now display the upload limit if it is defined. This was
done with localization in mind.

Lastly, the
[downloader.js](e52fc0e478/src/main/resources/static/js/downloader.js)
and
[fileInput.js](e52fc0e478/src/main/resources/static/js/fileInput.js)
files to include logic to enforce the upload limit if it is defined.

The UI updates, when the upload limit is defined, are as so:
<img width="708" alt="image"
src="https://github.com/user-attachments/assets/4852fa10-2ec3-45cb-83e6-41a102f256d4"
/>

When the limit is disabled, the page looks exactly as it did before any
implementation:
<img width="707" alt="image"
src="https://github.com/user-attachments/assets/21e5e810-ffdc-4a99-a16d-491aea103709"
/>\\

Thank you.

Closes #2903

---

## 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/DeveloperGuide.md)
(if applicable)
- [x] 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)
- [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)
- [x] 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)

- [x] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [x] 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.

---------

Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

src/main/resources/settings.yml.template

@@ -110,6 +110,7 @@ system:
     operations:
       weasyprint: '' #Defaults to /opt/venv/bin/weasyprint
       unoconvert: '' #Defaults to /opt/venv/bin/unoconvert
+  fileUploadLimit: '' # Defaults to "". No limit when string is empty. Set a number, between 0 and 999, followed by one of the following strings to set a limit. "KB", "MB", "GB".
 
 ui:
   appName: '' # application's visible name