JWT enhancements for desktop (#5742)

# Description of Changes

This is temporary solution which will be enhanced in future

---

## 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/public/locales/en-GB/translation.toml

@@ -1236,9 +1236,21 @@ label = "Enable Key Cleanup"
 description = "Automatically rotate JWT signing keys periodically"
 label = "Enable Key Rotation"
 
-[admin.settings.security.jwt.keyRetentionDays]
-description = "Number of days to retain old JWT keys for verification"
-label = "Key Retention Days"
+[admin.settings.security.jwt.tokenExpiryMinutes]
+description = "Access token lifetime in minutes for web clients (default: 1440 = 24 hours)"
+label = "Web Token Expiry (minutes)"
+
+[admin.settings.security.jwt.desktopTokenExpiryMinutes]
+description = "Access token lifetime in minutes for desktop clients. Desktop apps automatically detected via User-Agent and receive longer sessions for better UX (default: 43200 = 30 days)"
+label = "Desktop Token Expiry (minutes)"
+
+[admin.settings.security.jwt.allowedClockSkewSeconds]
+description = "Tolerance for client/server time drift during token validation (default: 60 seconds)"
+label = "Clock Skew Tolerance (seconds)"
+
+[admin.settings.security.jwt.refreshGraceMinutes]
+description = "Allow token refresh within this many minutes after expiry (default: 15 minutes, max 3 attempts)"
+label = "Refresh Grace Period (minutes)"
 
 [admin.settings.security.jwt.persistence]
 description = "Store JWT keys persistently to survive server restarts"