Import rollback_if_postgres in strategy_db for PostgreSQL migrations.

Co-authored-by: Cursor <cursoragent@cursor.com>

strategy/strategy_db.py

@@ -6,6 +6,8 @@
 """策略相关表结构。"""
 from __future__ import annotations
 
+from db_conn import rollback_if_postgres
+
 ROLL_GROUPS_SQL = """
 CREATE TABLE IF NOT EXISTS roll_groups (
     id INTEGER PRIMARY KEY AUTOINCREMENT,