feat: medium priority improvements

- Add 30 edge case tests (zero volume, empty data, extreme values,
  strategy reset, notifier failures)
- Fix VWAP division by zero on zero-price candles
- Add DB transaction rollback on errors + transaction() context manager
- Add parameter validation to all 7 strategies with 41 validation tests
- Fix lint issues across test files

1 files changed, 8 insertions, 6 deletions

diff --git a/services/strategy-engine/tests/test_strategy_validation.py b/services/strategy-engine/tests/test_strategy_validation.py
index a832a15..debab1f 100644
--- a/services/strategy-engine/tests/test_strategy_validation.py
+++ b/services/strategy-engine/tests/test_strategy_validation.py
@@ -204,12 +204,14 @@ class TestVwapValidation:
 class TestVolumeProfileValidation:
     def test_valid_params(self):
         s = VolumeProfileStrategy()
-        s.configure({
-            "lookback_period": 100,
-            "num_bins": 50,
-            "value_area_pct": 0.7,
-            "quantity": "0.01",
-        })
+        s.configure(
+            {
+                "lookback_period": 100,
+                "num_bins": 50,
+                "value_area_pct": 0.7,
+                "quantity": "0.01",
+            }
+        )
 
     def test_lookback_too_small(self):
         s = VolumeProfileStrategy()