Add Xquik import helpers

[kriptoburak]

Summary

• add TypeScript helpers that normalize Xquik bookmark records into MarkHarbor XBookmark objects
• cover author handles, URL fallback, media, link cards, and empty-record filtering with Vitest

Checks

• npm test -- src/shared/xquikImport.test.ts
• npm run typecheck
• git diff --check
• duplicate checks: memory ledger, default branch grep, all-state PR list, and exact PR/issue search for Xquik returned no existing placement