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/20260728060433_add_yoco_fee_fields_to_payment/migration.sql

@@ -0,0 +1,5 @@
+-- AlterTable
+ALTER TABLE "Payment" ADD COLUMN     "feeAmount" DOUBLE PRECISION,
+ADD COLUMN     "feeChannel" TEXT,
+ADD COLUMN     "feePayer" TEXT,
+ADD COLUMN     "feeRate" DOUBLE PRECISION;

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

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

backend/prisma/migrations/20260728070306_remove_fee_payer_fields/migration.sql

@@ -0,0 +1,12 @@
+/*
+  Warnings:
+
+  - You are about to drop the column `feePayerOnline` on the `Event` table. All the data in the column will be lost.
+  - You are about to drop the column `feePayer` on the `Payment` table. All the data in the column will be lost.
+
+*/
+-- AlterTable
+ALTER TABLE "Event" DROP COLUMN "feePayerOnline";
+
+-- AlterTable
+ALTER TABLE "Payment" DROP COLUMN "feePayer";

backend/prisma/migrations/20260728085349_add_fee_amount_to_cashup_line/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "EventCashupLine" ADD COLUMN     "feeAmount" DOUBLE PRECISION;

backend/prisma/schema.prisma

@@ -221,6 +221,9 @@ model Payment {
   externalId        String?           @unique
   status            String?
   originalPaymentId String?
+  feeAmount         Float?
+  feeRate           Float?
+  feeChannel        String?
   createdAt         DateTime          @default(now())
   user              User              @relation(fields: [userId], references: [id], onDelete: Restrict)
   registration      Registration?     @relation(fields: [registrationId], references: [id], onDelete: SetNull)
@@ -461,6 +464,7 @@ model EventCashupLine {
   cashup         EventCashup               @relation(fields: [cashupId], references: [id], onDelete: Cascade)
   method         String
   expectedAmount Float                     @default(0)
+  feeAmount      Float?
   actualAmount   Float?
   variance       Float?
   notes          String?