chore(ci): pinned actions versions

[CorentinTh]

No description provided.

[Copilot]

Pull Request Overview

This PR pins GitHub Actions to specific commit hashes instead of using version tags, improving security and reproducibility by preventing potential supply chain attacks through compromised action versions.

• Updated actions/checkout from v4 to v5 with pinned commit hash
• Replaced manual pnpm enablement with dedicated pnpm/action-setup action
• Updated actions/setup-node from v4 to v5 with pinned commit hash

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