feat: admin purge --boards wipes the board inventory behind a [y/N] gate - #7

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683, Swatinem/rust-cache@f13886b937689c021905a6b90929199931d60db1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/