feat(toolset): 工具系统重构为 toolset 统一管理，新增系统预置工具集

将工具管理从"agent 挂单个 tool"改为"agent 挂 toolset"模式：
- 三个系统预置工具集（system_basic/system_chat/system_workflow）入 DB
- 新增 send_file 工具（系统对话工具集）、修复 approval actor 调用 bug
- 后端 agent 加载全部走 toolset 链路，移除 load_tools_from_list
- 前端工具集中心卡片展示 + agent 配置改为 toolset 多选
- resource API 增加 category 过滤与系统 toolset 保护

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

kilostar/plugin/tool_plugin/send_file/__init__.py

@@ -0,0 +1,17 @@
+#  Copyright 2026 zhaoxi826
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+from .send_file import SendFileToolData, send_file
+
+__all__ = ["SendFileToolData", "send_file"]