[WIP] Fix/cookies jar submit #2668

[Sushanth012]

Summary

Fixes the cookie TODO in maigret/submit.py (line 218), part of #2668.

Changes

• check_features_manually now accepts cookie_filename, loads the
  cookie jar, filters cookies for both existing and generated URLs,
  and passes them into the HTTP comparison calls
• get_html_response_to_compare now forwards optional cookies to
  session.get
• Added a regression test in tests/test_submit.py confirming the
  cookie jar is loaded and filtered for both URLs

Closes part of #2668

[soxoj]

Hi @Sushanth012, thanks a lot for picking up sub-task 1 from #2668 — the cookie plumbing through check_features_manually looks correct and the regression test is well-scoped. I'd like to land that part 👍 🆒

However, this PR also contains a second, unrelated commit — "Improve graph visualization: dark theme, node info, linking" — which is not mentioned in the title or description and touches ~150 lines in maigret/report.py. Could you please split the PR into two:

1. Cookies PR — keep only the submit.py + tests/test_submit.py changes from this branch. I'm happy to merge that once it's isolated.

2. Graph visualization PR — open separately, with before/after screenshots and a short rationale.

Splitting the work makes both changes much easier to review, and lets the cookie fix land immediately while we iterate on the visualization. Thanks again for the contribution! 👍