ci: add manual dependency updates workflow

[daggerok]

Summary

• add a manually triggered dependency update workflow
• keep npm-check-updates verification in the main CI workflow
• make npm test run npm run build so CI does not fail because there are no tests yet
• keep GitHub Pages deploys available for branch testing
• simplify the manual update flow to match the existing repo style: commit/push with normal git, then explicitly trigger Pages deploy

Commit identity

All commits in this branch use:

• Maksim Kostromin <daggerok@gmail.com>

Notes

• this branch supersedes the earlier temporary branch/PR experiment
• the manual dependency workflow now avoids PAT-specific complexity and explicitly triggers github-pages.yml after dependency changes are pushed

Validation

• build workflow passes on branch
• dependency update workflow was rerun successfully on the branch
• GitHub Pages workflow was triggered successfully for the branch