Fix djlint findings in index.jinja2 so pre-commit passes

[contputer0x0]

Problem

pre-commit.ci currently fails on open PRs at the djlint hook, which reports 7 findings in src/pytest_html/resources/index.jinja2. The findings are pre-existing (not introduced by any particular PR): the djlint hook is declared with additional_dependencies: [djlint] (unpinned), so as newer djlint releases tightened their rule set, the template started tripping checks that earlier cached runs on master did not. The result is that unrelated PRs get a red pre-commit.ci.

What this does

Fixes the real findings and ignores the two that are intentional:

• H024 – drop the redundant type="text/css" on <style> and <link> (not needed in HTML5).
• H043 – add type="button" to the Show all details / Hide all details buttons so they don't default to submit.
• H056 / H057 – add to the existing [tool.djlint] ignore list, with a comment: the media <img>/<source> src is intentionally empty and populated at runtime by report.js, and the <video> has no caption source to track.

Verification

• djlint src/pytest_html/resources/index.jinja2 --profile jinja with the updated ignore list: 0 errors (was 7).
• The change is internal/tooling only; rendered reports are unaffected (removing type="text/css" and adding type="button" do not change behavior). The existing legacy_test_pytest_html.py stylesheet-link assertion checks rel="stylesheet" without type, so it still matches.