fix: ensure systemd service file is created during updates

- Added setup_systemd_service call to perform_update() function
- Fixes issue where service file could be missing after updates
- Now updates will recreate pulse.service if it doesn't exist

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/install-pulse.sh

@@ -633,6 +633,7 @@ perform_update() {
     fi
     
     set_permissions
+    setup_systemd_service
     
     # Restart service
     systemctl start "$SERVICE_NAME"