migrate session handling to aioweb_tls/refactoring of helpers

tests/test_price_before_drop.py

@@ -1,7 +1,7 @@
 """unit test: resolve_price_before_drop detects a drop from the prior stored price
 
 run from the repo root:
-    uv run python tests/test_price_before_drop.py
+    uv run pytest tests/test_price_before_drop.py
 
 pure and offline — no Mongo, no product construction; just the drop rule
 add_products_to_database relies on
@@ -23,8 +23,3 @@ def test_non_drops_return_none():
     assert resolve_price_before_drop(150.0, 150.0) is None  # unchanged
     assert resolve_price_before_drop(150.0, 200.0) is None  # price rose
     assert resolve_price_before_drop(200.0, None) is None  # missing new price
-
-
-test_drop_returns_previous_price()
-test_non_drops_return_none()
-print("price before drop test passed")