chore: bump GitHub Actions to latest stable versions

[claude]

Bumps tag-pinned GitHub Actions to their latest stable major-version releases. SHA-pinned actions were left untouched (intentionally pinned for supply-chain security).

Changes:

• aieo-content-reusable.yml: actions/checkout@v4 -> actions/checkout@v7
• aieo-content-reusable.yml: actions/checkout@v4 -> actions/checkout@v7
• aieo-content-reusable.yml: actions/setup-python@v5 -> actions/setup-python@v7
• aieo-content-reusable.yml: actions/upload-artifact@v4 -> actions/upload-artifact@v7
• ci.yml: actions/checkout@v4 -> actions/checkout@v7
• ci.yml: actions/setup-python@v5 -> actions/setup-python@v7
• ci.yml: codecov/codecov-action@v5 -> codecov/codecov-action@v7
• ci.yml: actions/checkout@v4 -> actions/checkout@v7
• ci.yml: actions/setup-node@v4 -> actions/setup-node@v7
• ci.yml: actions/checkout@v4 -> actions/checkout@v7
• ci.yml: actions/setup-python@v5 -> actions/setup-python@v7
• claude.yml: actions/checkout@v4 -> actions/checkout@v7
• markdown-oneline.yml: actions/checkout@v4 -> actions/checkout@v7
• markdown-oneline.yml: actions/setup-python@v5 -> actions/setup-python@v7
• release.yml: actions/checkout@v4 -> actions/checkout@v7
• release.yml: actions/setup-node@v4 -> actions/setup-node@v7

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Generated by Claude Code

[claude]

CI failure on lint (ruff check backend/ → 754 pre-existing violations, e.g. UP007/UP035/UP006 typing-modernization rules and B904 aliased-exception rules across many files) is pre-existing and unrelated to this PR's changes — this PR only touches .github/workflows/*.yml.

Root cause: the lint job installs ruff unpinned (pip install black==25.11.0 ruff mypy), while black is pinned. lint passed on main's last recorded run, but a newer ruff release since then now flags rules it didn't before — this would fail identically on main if re-run today, regardless of this PR.

frontend-tests and backend-tests both pass.

Fixing this means either pinning ruff to a known-good version or doing a real lint cleanup across the backend — an application-code decision out of scope for this CI-chore PR. Flagging as a separate pre-existing issue rather than pushing an unrelated fix here.

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Generated by Claude Code