docs: add Performance & Caching section to ConfigurationGuide

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_database_indexes.py

@@ -3,8 +3,7 @@ Tests for database performance indexes and schema migrations.
 """
 
 import pytest
-from sqlalchemy import create_engine, inspect, text
-from sqlalchemy.orm import sessionmaker
+from sqlalchemy import create_engine, inspect
 from sqlalchemy.pool import StaticPool
 
 from app.database import Base, _ensure_indexes