fix: ensure service file exists even when version is current

- Added setup_systemd_service to "already latest version" path in updates
- Fixes case where service file is missing but version check passes
- Now recreates service file in all update scenarios

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

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

scripts/install-pulse.sh

@@ -608,6 +608,7 @@ perform_update() {
     local current_version=$(get_current_version)
     if [ "$current_version" = "${TARGET_TAG#v}" ]; then
         print_info "Already running latest version"
+        setup_systemd_service
         systemctl start "$SERVICE_NAME"
         return 0
     fi