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/src-tauri/src/utils/logging.rs

@@ -0,0 +1,90 @@
+use std::sync::Mutex;
+use std::collections::VecDeque;
+use std::fs::OpenOptions;
+use std::io::Write;
+use std::path::PathBuf;
+
+// Store backend logs globally
+static BACKEND_LOGS: Mutex<VecDeque<String>> = Mutex::new(VecDeque::new());
+
+// Get platform-specific log directory
+fn get_log_directory() -> PathBuf {
+    if cfg!(target_os = "macos") {
+        // macOS: ~/Library/Logs/Stirling-PDF
+        let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
+        PathBuf::from(home).join("Library").join("Logs").join("Stirling-PDF")
+    } else if cfg!(target_os = "windows") {
+        // Windows: %APPDATA%\Stirling-PDF\logs
+        let appdata = std::env::var("APPDATA").unwrap_or_else(|_| std::env::temp_dir().to_string_lossy().to_string());
+        PathBuf::from(appdata).join("Stirling-PDF").join("logs")
+    } else {
+        // Linux: ~/.config/Stirling-PDF/logs
+        let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
+        PathBuf::from(home).join(".config").join("Stirling-PDF").join("logs")
+    }
+}
+
+// Helper function to add log entry
+pub fn add_log(message: String) {
+    let timestamp = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap()
+        .as_secs();
+    
+    let log_entry = format!("{}: {}", timestamp, message);
+    
+    // Add to memory logs
+    {
+        let mut logs = BACKEND_LOGS.lock().unwrap();
+        logs.push_back(log_entry.clone());
+        // Keep only last 100 log entries
+        if logs.len() > 100 {
+            logs.pop_front();
+        }
+    }
+    
+    // Write to file
+    write_to_log_file(&log_entry);
+    
+    // Remove trailing newline if present
+    let clean_message = message.trim_end_matches('\n').to_string();
+    println!("{}", clean_message); // Also print to console
+}
+
+// Write log entry to file
+fn write_to_log_file(log_entry: &str) {
+    let log_dir = get_log_directory();
+    if let Err(e) = std::fs::create_dir_all(&log_dir) {
+        eprintln!("Failed to create log directory: {}", e);
+        return;
+    }
+    
+    let log_file = log_dir.join("tauri-backend.log");
+    
+    match OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(&log_file)
+    {
+        Ok(mut file) => {
+            if let Err(e) = writeln!(file, "{}", log_entry) {
+                eprintln!("Failed to write to log file: {}", e);
+            }
+        }
+        Err(e) => {
+            eprintln!("Failed to open log file {:?}: {}", log_file, e);
+        }
+    }
+}
+
+// Get current logs for debugging
+pub fn get_logs() -> Vec<String> {
+    let logs = BACKEND_LOGS.lock().unwrap();
+    logs.iter().cloned().collect()
+}
+
+// Command to get logs from frontend
+#[tauri::command]
+pub async fn get_tauri_logs() -> Result<Vec<String>, String> {
+    Ok(get_logs())
+}

frontend/src-tauri/src/utils/mod.rs

@@ -0,0 +1,3 @@
+pub mod logging;
+
+pub use logging::{add_log, get_tauri_logs};