authclient (#5761)

# Description of Changes

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- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## 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/devGuide/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 tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

frontend/src-tauri/src/commands/auth.rs

@@ -336,6 +336,7 @@ pub async fn login(
     let client = reqwest::Client::builder()
         .danger_accept_invalid_certs(true)
         .timeout(std::time::Duration::from_secs(30))
+        .user_agent("StirlingPDF-Desktop/1.0 Tauri")
         .build()
         .map_err(|e| {
             log::error!("Failed to create HTTP client: {}", e);
@@ -689,6 +690,7 @@ async fn exchange_code_for_token(
     let client = reqwest::Client::builder()
         .danger_accept_invalid_certs(true)
         .timeout(std::time::Duration::from_secs(30))
+        .user_agent("StirlingPDF-Desktop/1.0 Tauri")
         .build()
         .map_err(|e| {
             log::error!("Failed to create HTTP client: {}", e);

frontend/src/desktop/services/authService.ts

@@ -4,6 +4,7 @@ import { open as shellOpen } from '@tauri-apps/plugin-shell';
 import { connectionModeService } from '@app/services/connectionModeService';
 import { tauriBackendService } from '@app/services/tauriBackendService';
 import axios from 'axios';
+import tauriHttpClient from '@app/services/tauriHttpClient';
 import { DESKTOP_DEEP_LINK_CALLBACK, STIRLING_SAAS_URL, SUPABASE_KEY } from '@app/constants/connection';
 
 export interface UserInfo {
@@ -559,8 +560,9 @@ export class AuthService {
         return false;
       }
 
-      // Call the server's refresh endpoint
-      const response = await axios.post(
+      // Call the server's refresh endpoint using Tauri HTTP client so the desktop
+      // User-Agent is sent - the backend uses it to issue long-lived desktop tokens.
+      const response = await tauriHttpClient.post(
         `${serverUrl}/api/v1/auth/refresh`,
         {},
         {

frontend/src/desktop/services/tauriHttpClient.ts

@@ -59,7 +59,9 @@ interface Interceptors {
 class TauriHttpClient {
   public defaults: TauriHttpRequestConfig = {
     baseURL: '',
-    headers: {},
+    headers: {
+      'User-Agent': 'StirlingPDF-Desktop/1.0 Tauri',
+    },
     timeout: 120000,
     responseType: 'json',
     withCredentials: false, // Desktop doesn't need credentials (backend has allowCredentials=false)