fix: ensure the tenant-scoped collection in upsert_document_chunks

ensure_collection() was called with the raw user string while the
upsert targeted get_collection_name(user), creating stray bare-name
collections (e.g. 'test_user') and failing the actual upsert when the
scoped collection did not exist yet.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/clients/qdrant_client.py

@@ -137,7 +137,9 @@ class QdrantClientWrapper:
             )
 
         collection_name = self.get_collection_name(user)
-        await self.ensure_collection(user)
+        # Ensure the tenant-scoped collection (passing the raw user here used
+        # to create a stray collection named after the bare user string).
+        await self.ensure_collection(collection_name)
 
         points = []
         for i, (chunk, embedding) in enumerate(zip(chunks, embeddings)):