feat(paperless-ai): enable intelligent timeline tagging with date extraction
- Add ENABLE_INTELLIGENT_TAGGING for advanced AI-powered tagging
- Add ENABLE_DATE_EXTRACTION for automatic date/timeline parsing
- Add ENABLE_TIMELINE_TAGGING to create temporal tags (YYYY, Q#-YYYY, Last-Month, etc)
- Set TAG_EXTRACTION_MODEL to reasoning for sophisticated analysis
- Configure timeline granularity (year, quarter, month)
- Add custom prompt for temporal context extraction
- Auto-create tags for historical and recent documents