Revert: do not auto-set membership_type on enrollment

Membership is only for participants who explicitly registered with a
membership_id. Non-members pay 900, members pay 650 — determined at
registration time, not at enrollment.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Domain/Training/Services/EnrollmentService.php

@@ -95,16 +95,9 @@ public function enroll(Participant $participant, TrainingGroup $group, User $act
             // Update group count
             $this->groupService->incrementCount($group);
 
-            // Activate participant and set as member on first enrollment
-            $updates = [];
+            // Activate participant if still in registered status
             if ($participant->status->value === 'registered') {
-                $updates['status'] = 'active';
-            }
-            if (($participant->membership_type?->value ?? $participant->membership_type) === 'non_member') {
-                $updates['membership_type'] = 'member';
-            }
-            if ($updates) {
-                $participant->update($updates);
+                $participant->update(['status' => 'active']);
             }
 
             // Auto-create invoice if program has a price (skip if invoice already provided via options)