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/desktop/contexts/AppConfigContext.tsx

@@ -0,0 +1,135 @@
+import React, { createContext, useContext, useState, useEffect } from 'react';
+import apiClient from '@app/services/apiClient';
+
+// Retry configuration
+const MAX_RETRIES = 5;
+const INITIAL_DELAY = 1000; // 1 second
+
+/**
+ * Sleep utility for delays
+ */
+function sleep(ms: number): Promise<void> {
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+export interface AppConfig {
+  baseUrl?: string;
+  contextPath?: string;
+  serverPort?: number;
+  appNameNavbar?: string;
+  languages?: string[];
+  enableLogin?: boolean;
+  enableEmailInvites?: boolean;
+  isAdmin?: boolean;
+  enableAlphaFunctionality?: boolean;
+  enableAnalytics?: boolean | null;
+  enablePosthog?: boolean | null;
+  enableScarf?: boolean | null;
+  premiumEnabled?: boolean;
+  premiumKey?: string;
+  termsAndConditions?: string;
+  privacyPolicy?: string;
+  cookiePolicy?: string;
+  impressum?: string;
+  accessibilityStatement?: string;
+  runningProOrHigher?: boolean;
+  runningEE?: boolean;
+  license?: string;
+  SSOAutoLogin?: boolean;
+  serverCertificateEnabled?: boolean;
+  error?: string;
+}
+
+interface AppConfigContextValue {
+  config: AppConfig | null;
+  loading: boolean;
+  error: string | null;
+  refetch: () => Promise<void>;
+}
+
+// Create context
+const AppConfigContext = createContext<AppConfigContextValue | undefined>(undefined);
+
+/**
+ * Provider component that fetches and provides app configuration
+ * Should be placed at the top level of the app, before any components that need config
+ */
+export const AppConfigProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
+  const [config, setConfig] = useState<AppConfig | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  const fetchConfig = async () => {
+    setLoading(true);
+    setError(null);
+
+
+    for (let attempt = 0; attempt <= MAX_RETRIES; attempt++) {
+      try {
+        if (attempt > 0) {
+          const delay = INITIAL_DELAY * Math.pow(2, attempt - 1);
+          console.log(`[AppConfig] Retry attempt ${attempt}/${MAX_RETRIES} after ${delay}ms delay...`);
+          await sleep(delay);
+        } else {
+          console.log('[AppConfig] Fetching app config...');
+        }
+
+        const response = await apiClient.get<AppConfig>('/api/v1/config/app-config');
+
+        setConfig(response.data);
+        console.log('[AppConfig] Successfully fetched app config');
+        setLoading(false);
+        return; // Success - exit function
+      } catch (err: any) {
+        const status = err?.response?.status;
+
+        // Check if we should retry (network errors or 5xx errors)
+        const shouldRetry = (!status || status >= 500) && attempt < MAX_RETRIES;
+
+        if (shouldRetry) {
+          console.warn(`[AppConfig] Attempt ${attempt + 1} failed (status ${status || 'network error'}):`, err.message, '- will retry...');
+          continue;
+        }
+
+        // Final attempt failed or non-retryable error (4xx)
+        const errorMessage = err?.response?.data?.message || err?.message || 'Unknown error occurred';
+        setError(errorMessage);
+        console.error(`[AppConfig] Failed to fetch app config after ${attempt + 1} attempts:`, err);
+        break;
+      }
+    }
+
+    setLoading(false);
+  };
+
+  useEffect(() => {
+    fetchConfig();
+  }, []);
+
+  const value: AppConfigContextValue = {
+    config,
+    loading,
+    error,
+    refetch: fetchConfig,
+  };
+
+  return (
+    <AppConfigContext.Provider value={value}>
+      {children}
+    </AppConfigContext.Provider>
+  );
+};
+
+/**
+ * Hook to access application configuration
+ * Must be used within AppConfigProvider
+ */
+export function useAppConfig(): AppConfigContextValue {
+  const context = useContext(AppConfigContext);
+
+  if (context === undefined) {
+    throw new Error('useAppConfig must be used within AppConfigProvider');
+  }
+
+  return context;
+}