Route docker_scanner error/troubleshooting output through docksec.output

[advaitpatel]

Summary

Follow-up cleanup: docker_scanner.py's Hadolint/Trivy/Docker Scout error and
troubleshooting messages used raw print() instead of the docksec.output layer used
everywhere else in the tool, so they didn't honor --quiet/--no-color/--json.

Changes

• Hadolint execution/timeout/not-found/unexpected-error paths: print() -> ui.error() +
  ui.detail() for troubleshooting steps.
• Trivy JSON scan failures (stderr, timeout, JSON decode, generic exception) and the
  legacy text-scan timeout/error paths: print() -> ui.error().
• Docker Scout advanced_scan() summary: print() -> ui.info()/ui.detail().
• Left the standalone main()/main block (python docker_scanner.py , a separate
  debug entry point) untouched - it's not part of the real docksec CLI and was out of
  scope for this cleanup.

Testing

• ruff check . passes.
• pytest: 157 passed (no behavior change, no new tests needed - purely an output-routing
  change).
• Manual runs verified error and normal output still render correctly for --image-only
  and --compose scans.