release: v4.2.0 — Entra directory role membership export

- Add Scripts/Export-EntraRoleMembership.ps1 to export active + PIM-eligible
  Entra directory role memberships (with group expansion) to CSV.
- Wire the new script into Start-IntuneToolkit.ps1 as menu item 20.
- Document the new script in README.md and AGENTS.md.
- Bump VERSION to 4.2.0 and add CHANGELOG entry.
- Harden .gitignore against local operational artifacts (accounts/ folder,
  deploy.sh, restart_gateways.sh).

.gitignore

@@ -36,3 +36,8 @@ __pycache__/
 *.pyo
 .venv-pdf/
 .venv/
+
+# Local operational artifacts that are not part of the toolkit
+accounts/
+deploy.sh
+restart_gateways.sh