fix: schedule_delete 外键约束导致无法删除定时任务

- schedule_delete_tool 执行前先解除 executions.schedule_id 引用
- 迁移 012: executions.schedule_id FK 改为 ON DELETE SET NULL

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/alembic/versions/012_schedule_fk_set_null.py

@@ -0,0 +1,43 @@
+"""alter executions.schedule_id FK to ON DELETE SET NULL
+
+Revision ID: 012_schedule_fk_set_null
+Revises: 011_add_agent_market_fields
+Create Date: 2026-05-07
+"""
+from alembic import op
+
+revision = "012_schedule_fk_set_null"
+down_revision = "011_add_agent_market_fields"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    """将 executions.schedule_id 外键改为 SET NULL，删除定时任务时自动保留执行记录。"""
+    try:
+        op.drop_constraint("executions_ibfk_3", "executions", type_="foreignkey")
+    except Exception:
+        # FK name may vary; try alternate patterns
+        try:
+            op.drop_constraint("executions_ibfk_4", "executions", type_="foreignkey")
+        except Exception:
+            pass
+    op.create_foreign_key(
+        "executions_ibfk_3",
+        "executions", "agent_schedules",
+        ["schedule_id"], ["id"],
+        ondelete="SET NULL",
+    )
+
+
+def downgrade() -> None:
+    try:
+        op.drop_constraint("executions_ibfk_3", "executions", type_="foreignkey")
+    except Exception:
+        pass
+    op.create_foreign_key(
+        "executions_ibfk_3",
+        "executions", "agent_schedules",
+        ["schedule_id"], ["id"],
+        ondelete="RESTRICT",
+    )

backend/app/services/builtin_tools.py

@@ -1894,6 +1894,11 @@ async def schedule_delete_tool(
                     }, ensure_ascii=False)
 
                 name = schedule.name
+                # 先将引用此 schedule 的 execution 记录的 schedule_id 置空，避免外键约束
+                from app.models.execution import Execution
+                db.query(Execution).filter(Execution.schedule_id == schedule_id).update(
+                    {Execution.schedule_id: None}, synchronize_session=False
+                )
                 db.delete(schedule)
                 db.commit()
                 db.close()
@@ -1915,6 +1920,12 @@ async def schedule_delete_tool(
 
                 names = [s.name for s in schedules]
                 count = len(schedules)
+                # 先解除所有 execution 记录的 schedule_id 外键引用
+                from app.models.execution import Execution
+                sids = [s.id for s in schedules]
+                db.query(Execution).filter(Execution.schedule_id.in_(sids)).update(
+                    {Execution.schedule_id: None}, synchronize_session=False
+                )
                 for s in schedules:
                     db.delete(s)
                 db.commit()