Add Yoco processing fee tracking to payments, settings, and reports

Estimates and snapshots the Yoco card-processing fee (always church-borne)
on every card payment, lets the admin configure in-person/online fee % per
plan in Settings -> Payments, and surfaces the fee alongside gross revenue
across the Finance/Profit reports, Master Orders, Revenue Detailed, and the
full cashup reconciliation flow (close-out screen, Cashup report, and audit
trail) so payout figures match what actually lands in the bank.

backend/prisma/migrations/20260728065200_add_event_fee_payer_override/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "Event" ADD COLUMN     "feePayerOnline" TEXT;