feat: Now Playing button + picker + Recent Listens on dashboard

[eboudrant]

Summary

Phase 3 (final) of the Listens feature. The dashboard now has the primary entry point: a Now Playing button that opens a collection picker + a Recent Listens cover strip.

This PR's diff currently includes PR #105 (detail-panel listens) since it's branched off it. Once PR #105 merges into `main`, this diff will collapse to only the Phase 3 changes.

• New `#dash-now-playing-section` above Random Picks: full-width primary button + Recent Listens strip (up to 8 covers, newest first).
• New `#picker-modal`: filter input over your collection, tap a record to log + close + toast.
• 9 new i18n keys per locale.
• Playwright: new `dashboard-now-playing.png` + `picker-modal.png` baselines. Shifted baselines for `dashboard.png`, `dashboard-empty.png`, and setup-wizard screenshots regenerated.
• Fixture: unfiltered `GET /api/listens` now returns the flattened list so the strip populates in tests.

Test plan

• `npm run test:screenshots` → 73 passed, 3 skipped.
• Chrome MCP verification did not run. Every `http://localhost:*\` nav in this session was blocked by a Chrome enterprise policy error ("This site is blocked by your organization's policy"). The Playwright test covers the same DOM surface. Please eyeball the preview tab once this is checked out locally.
• Visual review: picker modal on desktop + mobile looks right; covers arranged 2/3 cols.
• Language switch: open Now Playing modal, open Settings, switch to FR/JA/DE, close modal, reopen — confirm translated labels.

Not auto-merging

Per feedback: UI PRs need your review before landing.

🤖 Generated with Claude Code