1. Participant edit: guardian section now allows creating a new guardian
   (name + phone) OR selecting existing + editing phone. Checkbox toggles
   between modes.

2. Receptionist wizard: guardian name auto-fill now takes ALL names after
   the first (was only taking 2). "محمود أحمد عبد الفتاح علي" → guardian
   gets "أحمد عبد الفتاح علي" instead of just "أحمد عبد الفتاح".

3. Receptionist wizard step 5: added enrollment_start_date field so the
   user can specify when the player actually started (for accurate
   proration). Defaults to today if left empty.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>