fix: handle broken article links in bounty verifier

[answndud]

Refs #305.

Summary

• add a timeout to the bounty verifier article-link HEAD request
• follow redirects while checking article links
• treat network failures as a broken article link instead of crashing report generation

Bug

BountyVerifier.generate_report(..., article_url=...) currently calls requests.head(article_url) without a timeout or RequestException handling. A refused connection, DNS failure, invalid URL, or slow endpoint can raise out of report generation or hang the verifier instead of recording the article as broken.

Verification

• python3 -m py_compile tools/bounty-bot-pro/verifier.py
• python3 - <<'PY'\nimport ast\nfrom pathlib import Path\nast.parse(Path("tools/bounty-bot-pro/verifier.py").read_text())\nprint("parsed")\nPY\n- git diff --check -- tools/bounty-bot-pro/verifier.py\n\nNote: this branch is based on origin/main, so it still shows the pre-existing invalid-backtick SyntaxWarning that PR fix: remove invalid python escape warnings #4268 fixes separately. This PR is scoped only to the article-link request failure path.

[github-actions]

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[answndud]

Withdrawing this lower-impact PR to reduce review noise and focus the bounty submissions on higher-impact security/crash/behavior fixes.