- Add html-lint job to CI that runs djlint on all PRs
- Configure djlint in pyproject.toml with Jinja2 profile and accessibility rules
- Add djlint to requirements-dev.txt
- Expand accessibility section in frontend Copilot instructions (WCAG 2.1 AA)
- Wire html-lint into CI dependency chain (test/mypy/build depend on it)
Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>