fix: close DB session in run_step finally block

Wraps the SessionLocal body in try/finally so db.close() is always
called, preventing connection leaks on exception. Updates the
test monkeypatch to use a no-op close() proxy so the transactional
fixture stays live after run_step returns.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/orchestrator/runner.py

@@ -63,18 +63,21 @@ def run_step(step_name: str, week_start_date: Optional[date] = None) -> None:
 
     week = week_start_date or _current_week_start()
     db = SessionLocal()
-    families = db.query(FamilyProfile).all()
-    if not families:
-        logger.warning("run_step(%s): no family profiles, skipping", step_name)
-        return
-    for family in families:
-        run = _get_or_create_run(db, family.id, week)
-        try:
-            step_fns[step_name](run, db)
-        except Exception:
-            logger.exception(
-                "run_step(%s) failed for family %s", step_name, family.id
-            )
+    try:
+        families = db.query(FamilyProfile).all()
+        if not families:
+            logger.warning("run_step(%s): no family profiles, skipping", step_name)
+            return
+        for family in families:
+            run = _get_or_create_run(db, family.id, week)
+            try:
+                step_fns[step_name](run, db)
+            except Exception:
+                logger.exception(
+                    "run_step(%s) failed for family %s", step_name, family.id
+                )
+    finally:
+        db.close()
 
 
 def run_week(week_start_date: Optional[date] = None) -> None: