1. Program delete:
   - Removed delete button from program list (was broken)
   - Added red "حذف البرنامج" button inside program show page
   - Cascade deletes: sessions, schedules, enrollments, waitlists,
     assignments, groups — all force-deleted in one transaction

2. Trainer-group assignment:
   - GroupShow: assign/remove trainers via polymorphic assignments table
   - TrainerShow: assign/remove groups, shows all assigned groups
     (both head_trainer_id and assignments-based)
   - A trainer can be assigned to multiple groups
   - A group can have multiple trainers assigned
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>