重构代码，实现相对导入

rag_indexer/requirements.txt

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+# RAG Indexer - 本地索引工具依赖
+# 依赖 rag_core (从 ../backend/rag_core 导入)
+
+# Core
+pydantic==2.12.5
+python-dotenv==1.2.2
+typing-extensions==4.15.0
+
+# LangChain (用于文档处理)
+langchain==1.2.15
+langchain-community==0.4.1
+langchain-core==1.2.28
+tiktoken>=0.12.0
+
+# Vector DB
+qdrant-client==1.17.1
+
+# HTTP
+httpx==0.28.1
+
+# Utilities
+tenacity==9.1.4
+rich==15.0.0
+PyYAML==6.0.3
+numpy>=1.26.2
+
+# Document Processing
+unstructured==0.22.21
+pypdf==6.10.0
+beautifulsoup4==4.14.3
+lxml==6.1.0
+pandas==3.0.2
+spacy==3.8.14