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

backend/package.json

@@ -34,13 +34,14 @@
     "ajv": "^8.17.1",
     "axios": "^1.12.2",
     "dotenv": "^17.2.3",
+    "exceljs": "^4.4.0",
     "fastify": "^5.6.1",
     "form-data": "^4.0.4",
     "html2canvas": "^1.4.1",
     "js-yaml": "^4.1.0",
     "jsonrepair": "^3.13.1",
     "jspdf": "^3.0.3",
-    "p-queue": "^9.0.0",
+    "p-queue": "^9.0.1",
     "prisma": "^6.17.0",
     "tiktoken": "^1.0.22",
     "winston": "^3.18.3",