chore(ci): Maximize CI/CD values (Dependabot & Permissions)

[hyperpolymath]

This automated PR updates your CI/CD configurations to maximize value and security.

• Dependabot: Ensures github-actions is monitored for updates.
• Security: Adds permissions: read-all to workflows missing explicit permissions.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 9b72f7f900

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• Mark a draft as ready
• Comment "@codex review".

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Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Avoid enabling github-actions Dependabot before workflows pass lint

This new github-actions update block will generate PRs against .github/workflows/**, but the repo's own Workflow Security Linter runs on every such PR (.github/workflows/workflow-linter.yml:6-12) and currently rejects boj-build.yml because it still has no SPDX header (workflow-linter.yml:27-40 vs .github/workflows/boj-build.yml:1) and still uses an unpinned actions/checkout@v4 (workflow-linter.yml:61-77 vs boj-build.yml:11). In practice that means this automation will start producing daily action-update PRs that cannot go green or merge until the existing workflow is fixed or excluded.

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