ci: add contributor workflow automation

- Add PR template with description, type of change, and contributing checklist
- Enforce target branch: label + comment + 24h auto-close for PRs targeting main
- Flag bad issue titles: label + comment + 24h auto-close instead of instant close
- Redirect feature requests to Discussions (instant close, unchanged)
- Add two scheduled workflows to close stale labeled issues and PRs after 24h
- Update CONTRIBUTING.md with tests and branch up-to-date requirements

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,21 @@
+## Description
+<!-- What does this PR do? Why? -->
+
+## Related Issue or Discussion
+<!-- This project requires an issue or an approved feature request before submitting a PR. -->
+<!-- For bug fixes: Closes #ISSUE_NUMBER -->
+<!-- For features: Addresses discussion #DISCUSSION_NUMBER -->
+
+## Type of Change
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Breaking change
+- [ ] Documentation update
+
+## Checklist
+- [ ] I have read the [Contributing Guidelines](https://github.com/mauriceboe/TREK/wiki/Contributing)
+- [ ] My branch is [up to date with `dev`](https://github.com/mauriceboe/TREK/wiki/Development-environment#3-keep-your-fork-up-to-date)
+- [ ] This PR targets the `dev` branch, not `main`
+- [ ] I have tested my changes locally
+- [ ] I have added/updated tests that prove my fix is effective or that my feature works
+- [ ] I have updated documentation if needed