chore: bump medusa to 2.13.5 and mikro-orm to 6.4.16

Resolves version clash between plugin mikro-orm 6.4.3 and Medusa 2.13.5 which requires 6.4.16.

Closes #36

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

Author: dwene