style: apply black and isort formatting

Run formatting tools on Phase 1 changes:
- black (code formatter)
- isort (import sorter)
- ruff (linter)

All linting checks pass.

backend/tests/test_products_pricing.py

@@ -1,10 +1,11 @@
 import uuid
 
+from sqlmodel import select
+
 from innercontext.api import products as products_api
 from innercontext.models import PricingRecalcJob, Product
 from innercontext.models.enums import DayTime, ProductCategory
 from innercontext.services.pricing_jobs import process_one_pending_pricing_job
-from sqlmodel import select
 
 
 def _product(

backend/tests/test_routines_helpers.py

@@ -10,7 +10,6 @@ from innercontext.api.routines import (
     _build_products_context,
     _build_recent_history,
     _build_skin_context,
-    build_product_details_tool_handler,
     _contains_minoxidil_text,
     _ev,
     _extract_active_names,
@@ -18,6 +17,7 @@ from innercontext.api.routines import (
     _filter_products_by_interval,
     _get_available_products,
     _is_minoxidil_product,
+    build_product_details_tool_handler,
 )
 from innercontext.models import (
     GroomingSchedule,
@@ -444,7 +444,8 @@ def test_filter_products_by_interval():
     )
 
     last_used = {
-        str(p_interval_72.id): today - timedelta(days=1),  # used yesterday -> need 3 days
+        str(p_interval_72.id): today
+        - timedelta(days=1),  # used yesterday -> need 3 days
         str(p_interval_48.id): today - timedelta(days=3),  # used 3 days ago -> 48h ok
     }