Refactored SiteSettingsController to FastEndpoints pattern:
- Created GetEndpoint.cs: GET /api/sitesettings (authorized)
- Created SaveEndpoint.cs: PUT /api/sitesettings (authorized)
- Removed legacy SiteSettingsController.cs
Both endpoints use Bearer token authentication and are auto-discovered
by FastEndpoints configuration in Program.cs.
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
