Add desktop mobile-upload page and fix LAN QR URL (#6736)

# Description of Changes

Desktop can not use QR code upload due to API backend not having UI for
it...
Because of this we add UI, has to be custom because can not support
OpenCV and in app camera due to its https requirement

<img width="919" height="2048" alt="image"
src="https://github.com/user-attachments/assets/d84c3903-fd23-421a-8919-24d89ba6c753"
/>
<img width="919" height="2048" alt="image"
src="https://github.com/user-attachments/assets/d6c8fdf3-837b-4dc3-92ea-37f7502f8462"
/>
<img width="919" height="2048" alt="image"
src="https://github.com/user-attachments/assets/fd4ce3b4-69ad-45dd-b066-bff2d082c583"
/>

<img width="1550" height="790" alt="image"
src="https://github.com/user-attachments/assets/701d4dcc-ebd6-4e03-aa7b-2d8623525fc9"
/>

---

## 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/devGuide/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/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### 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 run `task check` to verify linters, typechecks, and tests
pass
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

.gitignore

@@ -49,6 +49,7 @@ app/core/src/main/resources/static/index.html
 # Prerendered per-route SPA pages (OG/social-preview), e.g. compress.html. api-landing.html is source.
 app/core/src/main/resources/static/*.html
 !app/core/src/main/resources/static/api-landing.html
+!app/core/src/main/resources/static/mobile-upload.html
 # Prerendered nested-route pages (e.g. settings/people.html)
 app/core/src/main/resources/static/settings/
 app/core/src/main/resources/static/locales/