Update GitHub Actions for Node 24

[plx]

Description

Updates pinned workflow actions to Node 24-compatible majors, removing GitHub runner deprecation warnings without changing job behavior.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Code refactoring
• Test improvements
• CI/CD improvements

Related Issues

None.

Motivation and Context

Recent CI and Pages run annotations identified Node 20 usage in Checkout v4, Setup Just v3's embedded Setup Crate action, Upload Pages Artifact v4's embedded Upload Artifact action, and Deploy Pages v4.

Implementation Details

Upgrades Checkout to v7, Setup Just to v4, Upload Pages Artifact to v5, and Deploy Pages to v5 across the affected workflows; upstream manifests for these replacements and their nested actions declare Node 24.

Testing

• All existing tests pass locally
• New tests added for new functionality
• Manual testing performed
• Integration tests pass
• Property-based tests pass (if applicable)
• Concurrency tests pass (if applicable)

Test Coverage

• actionlint .github/workflows/*.yml
• YAML parse validation
• git diff --check
• Repository-wide scan for remaining affected pins

Performance Impact

• No performance impact
• Performance improved
• Benchmarks run and results reviewed

Platform Compatibility

• Linux
• macOS
• Windows

Checklist

• Code follows the project's style guidelines (cargo fmt --check passes)
• No compiler warnings (cargo clippy passes)
• Self-review of code completed
• Comments added for complex logic
• Documentation updated (if applicable)
• CHANGELOG.md updated (if applicable)
• Tests added/updated and passing
• All CI checks passing

Database Migrations

• No database changes
• Database migrations included and tested
• Migration is reversible (if applicable)
• Migration tested with existing data

Breaking Changes

None.

Screenshots / Demo

Not applicable.

Additional Notes

Application tests were not run because this PR changes workflow configuration only.