* Add nightly build reproducibility checkbox
Add a required checkbox to the bug report template prompting reporters to verify the issue is reproducible in the latest nightly build (links to the nightly builds release). This helps catch issues already fixed in nightly releases and reduces duplicate reports.
* Add PR artifact download guide to template
Update the pull request template to include a commented section and a link to the OrcaSlicer wiki explaining how to download artifacts from a PR. This helps contributors and reviewers locate and retrieve build/test artifacts for verification and testing.
