🔧 fix: Ensure ShareView document title is configured

[arthurian]

Summary

This PR updates the document title on the shared link view to reflect the conversation title and application title. This will improve accessibility and link sharing/bookmarking.

Change Type

• [x] Bug fix (non-breaking change which fixes an issue)

Testing

Tested changes locally to confirm that the shared link view displays the conversation title and application title.

Steps:

1. Start a new conversation.
2. In the conversation panel, go to Export > Share
3. Click Create Link
4. Visit shared link.
5. Confirm that the document.title follows the format {conversationTitle} | {appTitle}.
   • The appTitle should match the configured APP_TITLE environment variable. Default is LibreChat if not configured.
   • The conversationTitle should match the displayed heading (h1).

Test Configuration:

Checklist

• [x] My code adheres to this project's style guidelines
• [x] I have performed a self-review of my own code
• [x] I have commented in any complex areas of my code
• [ ] I have made pertinent documentation changes
• [ ] My changes do not introduce new warnings
• [ ] I have written tests demonstrating that my changes are effective or that my feature works
• [ ] Local unit tests pass with my changes
• [ ] Any changes dependent on mine have been merged and published in downstream modules.
• [ ] A pull request for updating the documentation has been submitted.