feat(machine): persist exchange rate and currency in transactions

Add exchange_rate (sats per fiat unit) and currency columns to the
transactions table so transaction economics can be audited after the
fact. Includes schema migration v2 (fee columns) and v3 (rate/currency),
updated IPC types, and atm-transactions CLI output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/machine/src/stores/atm.ts

@@ -269,11 +269,22 @@ export const useAtmStore = defineStore('atm', () => {
             ? buildBillsFromInserted(ctx.billsInserted)
             : ctx.dispenseAmounts
 
+          // Compute fee in sats from context
+          const grossSats =
+            ctx.exchangeRate > 0 ? Math.floor((ctx.fiatCents / 100) * ctx.exchangeRate) : 0
+          const feeSats = isCashInTx
+            ? grossSats - ctx.satsAmount // cash-in: customer gets net (gross - fee)
+            : ctx.satsAmount - grossSats // cash-out: customer pays gross + fee
+
           persistTransaction({
             txid: ctx.txid,
             type: isCashInTx ? 'cash_in' : 'cash_out',
             fiatCents: ctx.fiatCents,
             sats: ctx.satsAmount,
+            feeSats: Math.max(0, feeSats),
+            feePercent: ctx.feePercent,
+            exchangeRate: ctx.exchangeRate,
+            currency: ctx.currency,
             bills,
           })
         }

apps/machine/src/types/electron.d.ts

@@ -40,6 +40,10 @@ declare global {
         type: 'cash_in' | 'cash_out'
         fiatCents: number
         sats: number
+        feeSats: number
+        feePercent: number
+        exchangeRate: number
+        currency: string
         bills: { denomination: number; count: number }[]
       }) => Promise<void>
       emptyCashbox: () => Promise<void>

apps/machine/src/types/state.ts

@@ -18,6 +18,10 @@ export interface TransactionRecord {
   type: 'cash_in' | 'cash_out'
   fiatCents: number
   sats: number
+  feeSats: number
+  feePercent: number
+  exchangeRate: number
+  currency: string
   bills: { denomination: number; count: number }[]
 }