Add pre-commit framework with insert-license hook to enforce SPDX headers

[janhoy]

Summary

There is currently no automated enforcement of the ASF SPDX license header on source files.
Add the pre-commit framework with the
insert-license hook so that every commit
automatically checks (and optionally inserts) the required header.

Motivation

• Apache Airflow uses this exact setup to enforce license headers across .py, .sh,
  .yaml, .xml, .md and more via per-type templates in
  scripts/ci/license-templates/
• Catches missing headers at commit time rather than at release time (when Apache RAT runs)
• ASF policy requires every source file to carry the SPDX Apache-2.0 header

Proposed changes

1. Add .pre-commit-config.yaml with Lucas-C/pre-commit-hooks insert-license hook
2. Add license header templates under scripts/ci/license-templates/ (one per file type)
3. Configure hooks for .py, .sh, .yaml/.yml, .toml, .cfg, .md
4. Add pre-commit to dev dependencies (or document pip install pre-commit && pre-commit install)
5. Add a make pre-commit target and run in CI

References

• https://pre-commit.com/
• https://github.com/Lucas-C/pre-commit-hooks