After the cashier collects the waiver fee, the system now automatically
executes the waiver completion (membership transfer) without requiring
a manual "إتمام التنازل" button click.

The auto-complete validates all conditions first:
- Fee paid (status = fee_paid)
- Target member specified
- Board approval exists
- No debts on source or target member
- Excess dependent fees properly set

If any condition fails, the waiver stays in fee_paid status with a
clear checklist showing what's still needed, plus a manual fallback
button for edge cases.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>