fix(mcp): add task_key/task_name to TaskInfo and strengthen test coverage

- Add task_key and task_name fields to TaskInfo schema and ALL_TASK_COLUMNS;
  these are real Task model columns present in the REST API search_columns
- Expand search_columns in list_tasks to include task_key and task_name
- Strengthen test_list_action_logs_default_7day_filter_applied to also
  assert the injected filter appears in filters_applied with an ISO string value

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