app-store: add Docker app card

[Alexgodoroja]

Adds a Docker card to the app-store page (and its plain-text twin), matching the existing native-tool cards.

• io.pilot.docker · Docker · v29.6.1 · Apache-2.0 · category devops
• Install: pilotctl appstore install io.pilot.docker
• 12 Methods · 87 MB · View source → github.com/moby/moby
• New logo asset public/brand/apps/docker.png (Docker whale mark).
• Plain twin updated and coverage re-stamped (check:plain passes); npm run build OK.

[github-actions]

🚀 Preview deployed to Cloudflare Pages

• Commit deploy URL: https://4a8a6238.pilotprotocol.pages.dev
• Branch alias: https://app-store-docker-card.pilotprotocol.pages.dev (may take ~30s to propagate)
• Commit: 42f86aa813c379917760098a9127801455f46a47