Prestige Barber Club v4.44.10 - Membership NET Dashboard Fix

ROOT CAUSE
Membership embedded in POS stored membership_sales.total_amount before the transaction-level member tier discount. Dashboard summed that gross membership amount, so a package such as Rp125,000 could still display as Rp125,000 even though the combined POS transaction received a member discount.

FIX
1. Standalone membership continues to use membership_sales.total_amount (already net membership-specific discounts).
2. Embedded POS membership uses transaction_membership_items.amount (already net card discount).
3. The transaction-level member discount + extra discount are allocated proportionally using transaction.discount_base_amount.
4. Dashboard Penjualan Member, Membership Reconciliation, and Membership Sales History display effective NET membership revenue.
5. Gross amount is preserved for audit; allocated transaction discount is displayed separately.
6. No historical transaction rows are destructively rewritten. The fix derives the correct effective net from existing ledger data.

FORMULA
Embedded membership NET = tmi.amount - tmi.amount * (member_discount_amount + extra_discount_amount) / discount_base_amount
(clamped at >= 0)