feat: guided 1,000+ interview question library - #15

What changed

• expands the attributed interview library to 1,029 unique questions
• imports 103 reviewed MIT-licensed questions from a pinned 30 Seconds of Interviews revision
• replaces the per-question dropdown with a guided session builder for goal, length, and challenge
• adds adaptive balancing, deterministic reshuffling, recent-question avoidance, and safe fallback for narrow filters
• keeps track, focus, and stage controls under optional fine-tuning
• documents provenance, licensing, sync steps, and future reviewed sources

Verification

• npm test: 84 passed
• npm run lint: 0 errors, 1 pre-existing BrandMark image warning
• production build passed
• git diff --check passed

Publishing

This is a Draft PR. Do not merge or deploy to Sites until explicitly approved.