chore(deps/docker): bump node from 18-alpine to 26-alpine - #847

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

'base' input parameter is ignored when action is triggered by pull request event and 'token' is provided - set token: '' to detect changes using git diff against 'base'