V2 Tauri integration (#3854)

# Description of Changes

Please provide a summary of the changes, including:

## Add PDF File Association Support for Tauri App

  ### 🎯 **Features Added**
  - PDF file association configuration in Tauri
  - Command line argument detection for opened files
  - Automatic file loading when app is launched via "Open with"
  - Cross-platform support (Windows/macOS)

  ### 🔧 **Technical Changes**
  - Added `fileAssociations` in `tauri.conf.json` for PDF files
  - New `get_opened_file` Tauri command to detect file arguments
  - `fileOpenService` with Tauri fs plugin integration
  - `useOpenedFile` hook for React integration
  - Improved backend health logging during startup (reduced noise)

  ### 🧪 **Testing**
See 
* https://v2.tauri.app/start/prerequisites/
*
[DesktopApplicationDevelopmentGuide.md](DesktopApplicationDevelopmentGuide.md)

  ```bash
  # Test file association during development:
  
  cd frontend
  npm install
  cargo tauri dev --no-watch -- -- "path/to/file.pdf"
  ```

 For production testing:
  1. Build: npm run tauri build
  2. Install the built app
  3. Right-click PDF → "Open with" → Stirling-PDF

  🚀 User Experience

- Users can now double-click PDF files to open them directly in
Stirling-PDF
- Files automatically load in the viewer when opened via file
association
  - Seamless integration with OS file handling

---

## 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.

---------

Co-authored-by: Connor Yoh <[email protected]>
Co-authored-by: James Brunton <[email protected]>
Co-authored-by: James Brunton <[email protected]>

frontend/README.md

@@ -72,3 +72,59 @@ This section has moved here: [https://facebook.github.io/create-react-app/docs/d
 ### `npm run build` fails to minify
 
 This section has moved here: [https://facebook.github.io/create-react-app/docs/troubleshooting#npm-run-build-fails-to-minify](https://facebook.github.io/create-react-app/docs/troubleshooting#npm-run-build-fails-to-minify)
+
+
+## Tauri
+In order to run Tauri, you first have to build the Java backend for Tauri to use.
+
+**macOS/Linux:**
+
+From the root of the repo, run:
+
+```bash
+./gradlew clean build
+./scripts/build-tauri-jlink.sh
+```
+
+**Windows**
+
+From the root of the repo, run:
+
+```batch
+gradlew clean build
+scripts\build-tauri-jlink.bat
+```
+
+### Testing the Bundled Runtime
+
+Before building the full Tauri app, you can test the bundled runtime:
+
+**macOS/Linux:**
+```bash
+./frontend/src-tauri/runtime/launch-stirling.sh
+```
+
+**Windows:**
+```cmd
+frontend\src-tauri\runtime\launch-stirling.bat
+```
+
+This will start Stirling-PDF using the bundled JRE, accessible at http://localhost:8080
+
+### Dev
+To run Tauri in development. Use the command in the `frontend` folder:
+
+```bash
+npm run tauri-dev
+```
+
+This will run the gradle runboot command and the tauri dev command concurrently, starting the app once both are stable.
+
+### Build
+To build a deployment of the Tauri app. Use this command in the `frontend` folder:
+
+```bash
+npm run tauri-build
+```
+
+This will bundle the backend and frontend into one executable for each target. Targets can be set within the `tauri.conf.json` file.