Add card DOM data attributes to printing-tag candidate buttons

[WilfordGrimley]

Summary

• Candidate printing buttons in the "Who's That Planeswalker?" queue (PrintingTagQueue.tsx) and picker (PrintingTagPicker.tsx) carried none of the documented card DOM API attributes (frontend/docs/dom-api.md), making them invisible to tooling built against that contract.
• Adds getPrintingCandidateDataAttributes in frontend/src/common/cardDom.ts (a PrintingCandidate-shaped sibling to getCardDataAttributes), spread onto the candidate <CandidateButton>/<Button> in both call sites, sourced from the card currently being tagged plus the PrintingCandidate for each button.
• PrintingTagPicker gained a cardName prop since it previously only had cardIdentifier; CardDetailedViewModal.tsx now passes cardDocument.name through.
• Documents the new attributes in dom-api.md, calling out explicitly that this is a different kind of hit than a normal card slot — data-card-name names the card being tagged, not necessarily what the candidate depicts.

Test plan

• npx tsc --noEmit clean
• npx eslint on changed files — 0 errors (pre-existing <img>-vs-next/image warnings only)
• npx prettier@2.7.1 --check clean
• npx playwright test tests/PrintingTagQueue.spec.ts tests/PrintingTagPicker.spec.ts --project=chromium — 7/7 passed (new assertions cover both files), including new tests asserting data-card-name/data-card-identifier/data-card-set-code/data-card-collector-number land on candidate buttons with correct values

🤖 Generated with Claude Code

[WilfordGrimley]

Landed directly on master (e2811ed) per this repo's standing direct-push workflow.