test(kb-accelerator): downgrade kb_setup user to free plan

The kb_setup fixture asserts free-plan quota numbers (lifetime_conversions_limit=3),
but Phase 1 conftest seeds test_user on Pro. Downgrade explicitly inside kb_setup
to preserve the original test intent without affecting other suites.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/tests/test_kb_accelerator.py

@@ -13,6 +13,14 @@ pytestmark = pytest.mark.asyncio
 @pytest.fixture
 async def kb_setup(client, auth_headers, test_db):
     """Seed KB plan limits and return helpers."""
+    # KB tests were authored against a free-plan user. Phase 1 conftest seeds
+    # the test_user with a pro/active Subscription; downgrade to free here so
+    # quota numbers match the original test intent.
+    from app.models.subscription import Subscription
+    sub = (await test_db.execute(__import__("sqlalchemy").select(Subscription))).scalar_one()
+    sub.plan = "free"
+    await test_db.commit()
+
     # Update plan_limits with KB columns for 'free' plan
     await test_db.execute(
         __import__("sqlalchemy").text("""