Qlib v0.9.8 released

Qlib v0.9.8 has been released, including security hardening completed at Microsoft's request, merging changes from #2339 and #2340. This version restricts the loading of executable recorder artifacts; loading artifacts from trusted storage requires explicitly setting trusted=True, and configuration-driven local .py imports also require explicitly enabling trusted: true. Before upgrading production workflows, please review the two migration guides. Source archives are available on GitHub, and PyPI packages can be queried separately.