feat(extraction): Phase 6 advanced features (6.1-6.8)
- 6.1-6.2: Entity visualization components (bar chart, pie chart, timeline) [in LysnrAI repo]
- 6.3-6.4: Async job queue — POST /extract/jobs, GET /extract/jobs/:id, GET /extract/jobs
- 6.5-6.6: Model registry with tier (standard/premium/free/mock) + GET /extract/models
- 6.7-6.8: Multi-language detection (es/fr/de/pt/ja/zh/ko/ar) + prompt enrichment
- ExtractMetadata.language field added to Python models
- 46 TS tests passing, build clean