patch Healtcheck

- Add optional PORT
- added `-n` to jq to return expected exit code when input is empty/null

Dockerfile

@@ -151,7 +151,7 @@ COPY --chown=$UID:$GID ./backend .
 
 EXPOSE 8080
 
-HEALTHCHECK CMD curl --silent --fail http://localhost:8080/health | jq -e '.status == true' || exit 1
+HEALTHCHECK CMD curl --silent --fail http://localhost:${PORT:-8080}/health | jq -ne 'input.status == true' || exit 1
 
 USER $UID:$GID