feat(web): show Product Hunt badge on welcome

[tyler-dane]

Summary

Adds the Product Hunt featured badge to the welcome guide so new users see it on first visit (and anyone who reopens the welcome guide).

The official embed is a native link + image with a visible focus ring. It sits in a full-width row under the intro copy so it centers in the modal (the welcome panel uses items-start, which left-aligned a nested badge).

Simplicity

One ProductHuntBadge component and a centered row in the existing welcome body. Dropped redundant mx-auto / w-fit on the link after the parent row already centers it. No extra state, effects, or refs.

Automated validation

• Welcome modal tests: 11 pass, including a role/name assertion for the Product Hunt link and href.
• bun run lint: no new findings (10 pre-existing warnings elsewhere).
• Manual: anonymous IndexedDB mode at http://localhost:9080 — badge loads and is horizontally centered with Start Now.

Independent review

Fresh read-only review of origin/main...HEAD: no confirmed findings. Native link, accessible name from alt, focus ring, noopener noreferrer, no storage/event-data changes.

Test plan

• bun test:web packages/web/src/components/WelcomeModal/WelcomeModal.test.tsx — 11 pass
• bun run lint
• Welcome modal visual check that the badge is centered