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

[kriptoburak]

If this is useful and you merge it after checks pass, feel free to share the PR on X/Twitter and mention my handle, burakbayir. I can repost or retweet it to my 24k followers of developers and power users, which may help more relevant users discover this repo.