refactor: 重构RAG核心组件，简化代码结构和测试文件

backend/rag_core/__init__.py

@@ -6,8 +6,13 @@ RAG Core - 公共 RAG 组件包
 from .embedders import get_embeddings, get_embedding_dimension
 from .vector_store import QdrantHybridStore
 from .sparse_embedder import BM25SparseEmbedder, get_sparse_embedder
-from .store import PostgresDocStore, create_docstore
-from .client import create_qdrant_client, create_async_qdrant_client
+from .doc_store import PostgresDocStore
+from .client import (
+    create_qdrant_client,
+    create_async_qdrant_client,
+    create_docstore,
+    get_docstore_uri
+)
 from .config import (
     QDRANT_URL,
     QDRANT_API_KEY,
@@ -24,14 +29,15 @@ __all__ = [
     "QdrantHybridStore",
     "BM25SparseEmbedder",
     "get_sparse_embedder",
+    "PostgresDocStore",
+    "create_docstore",
+    "get_docstore_uri",
+    "create_qdrant_client",
+    "create_async_qdrant_client",
     "QDRANT_URL",
     "QDRANT_API_KEY",
     "LLAMACPP_EMBEDDING_URL",
     "LLAMACPP_API_KEY",
     "DB_URI",
     "DOCSTORE_URI",
-    "PostgresDocStore",
-    "create_docstore",
-    "create_qdrant_client",
-    "create_async_qdrant_client",
 ]