Enable async_mode on PGVector for async method support

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

blueprints/rag/logic.py

@@ -38,6 +38,7 @@ def _get_vector_store() -> PGVector:
             connection=_pgvector_url,
             use_jsonb=True,
             create_extension=False,  # created by docker init script
+            async_mode=True,
         )
     return _vector_store
 
@@ -59,6 +60,7 @@ text_splitter = RecursiveCharacterTextSplitter(
 def _get_collection_id():
     """Get the UUID of our collection from the langchain_pg_collection table."""
     engine = _get_engine()
+    try:
         with engine.connect() as conn:
             result = conn.execute(
                 text("SELECT uuid FROM langchain_pg_collection WHERE name = :name"),
@@ -66,6 +68,9 @@ def _get_collection_id():
             )
             row = result.fetchone()
             return row[0] if row else None
+    except Exception:
+        # Table doesn't exist yet (first run before any indexing)
+        return None
 
 
 def date_to_epoch(date_str: str) -> float: