feat(asl): Complete Day 5 - Fulltext Screening Backend API Development

- Implement 5 core API endpoints (create task, get progress, get results, update decision, export Excel)
- Add FulltextScreeningController with Zod validation (652 lines)
- Implement ExcelExporter service with 4-sheet report generation (352 lines)
- Register routes under /api/v1/asl/fulltext-screening
- Create 31 REST Client test cases
- Add automated integration test script
- Fix PDF extraction fallback mechanism in LLM12FieldsService
- Update API design documentation to v3.0
- Update development plan to v1.2
- Create Day 5 development record
- Clean up temporary test files

docs/03-业务模块/ASL-AI智能文献/05-开发记录/2025-11-22_Day2-Day3_LLM服务与验证系统开发.md

@@ -605,3 +605,5 @@ npm install json-repair
 **状态**: ✅ Day 2 & Day 3 全部完成  
 **下一步**: Day 4 批处理任务服务
 
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