Fix concurrency: process-wide shared Qdrant client + per-op lock

src/cdms/document_loader.py

@@ -15,7 +15,7 @@ from datetime import datetime
 from src.cdms.pdf_processor import PDFProcessor
 from src.cdms.schema import DatabaseManager, Document, DocumentChunk
 from src.rag.embeddings import OpenAIEmbeddingService
-from src.rag.vector_store import QdrantVectorStore
+from src.rag.vector_store import QdrantVectorStore, get_shared_vector_store
 from src.config.credentials import CredentialsManager
 from src.config.paths import PDF_DIR
 from src.cdms.product_catalog import normalize_filename
@@ -59,12 +59,13 @@ class DocumentLoader:
             print(f"⚠️  Warning: Could not initialize OpenAI embeddings: {e}")
             self.embedding_service = None
         
-        # Reuse a shared vector store if provided (see docstring); else open one.
+        # Reuse the provided store, else the process-wide singleton (never open a
+        # second client to the embedded store — see get_shared_vector_store).
         if vector_store is not None:
             self.vector_store = vector_store
         else:
             try:
-                self.vector_store = QdrantVectorStore()
+                self.vector_store = get_shared_vector_store()
             except Exception as e:
                 print(f"⚠️  Warning: Could not initialize Qdrant: {e}")
                 self.vector_store = None