Merge remote changes with RAG service optimization

- Keep user's RAG service integration for faster extraction
- Add remote's word_ai_service support
- Preserve user's parallel extraction and field header optimizations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/services/template_fill_service.py

@@ -13,6 +13,7 @@ from app.services.llm_service import llm_service
 from app.core.document_parser import ParserFactory
 from app.services.markdown_ai_service import markdown_ai_service
 from app.services.rag_service import rag_service
+from app.services.word_ai_service import word_ai_service
 
 logger = logging.getLogger(__name__)