feat(tasks): 总览页支持任务测试范围的查看/增删

- db: 新增 DeleteTaskScope；AddAgentScope 加 source 参数区分 agent/manual
- server: 新增 POST/DELETE /api/tasks/{id}/scope 端点
- web: 总览页新增「测试范围」卡片，可按类型手动增删，继承范围只读

Claude-Session: https://claude.ai/code/session_014TfZWeVGhjXqZD3vcj44mz

agent/tools_insert.go

@@ -382,7 +382,7 @@ func (t *ToolSet) addTaskScope() actool.CoreTool {
 			var added []map[string]any
 			errs := map[string]string{}
 			for i, e := range items {
-				ts, err := t.as.AddAgentScope(t.taskID, strings.TrimSpace(e.Kind), e.Value, a.Reason)
+				ts, err := t.as.AddAgentScope(t.taskID, strings.TrimSpace(e.Kind), e.Value, a.Reason, "agent")
 				if err != nil {
 					errs[strconv.Itoa(i)] = err.Error()
 					continue