Extend AdminReserveSlotHandler's pre-overlap DELETE to also clean up anonymous RESERVATION:anon entries matching the admin's IP address. This handles the edge case where an admin previously reserved a slot without authentication. Also reorganise imports to follow goimports conventions. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>