Upgrade MegaLinter to v10.0.0

[FlorianPfaff]

What changed

• Updated .github/workflows/mega-linter.yml from oxsecurity/megalinter/flavors/python@v9.4.0 to @v10.0.0.
• Left all triggers, permissions, checkout behavior, and artifact handling unchanged.

Validation

• Compared the branch to dev: the cumulative diff is one file with one version-line substitution.
• MegaLinter 10 resolves and runs successfully.
• The current repository-wide lint baseline remains red with 32 Ruff errors and 17 yamllint errors; Markdown reports 25 non-blocking findings. Actionlint, repository git-diff validation, and YAML schema validation pass.
• Those findings are outside this cross-repository version-only upgrade and were not auto-fixed.