fix: correct bill denomination unit conversion and exchange rate

- Fix state machine to convert bill denominations from dollars to cents
  (e.g., $20 bill → 2000 cents in fiatAmount)
- Use fixed 1,000 sats/$ rate for development (~$100k BTC)
- Update test to expect correct cents value

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lamassu-next/apps/machine/src/services/lightning.ts

@@ -828,19 +828,12 @@ function createATMServices(
 
     /**
      * Get current exchange rate
+     * TODO: Fetch from Lightning.Pub or external price feed
      */
     getExchangeRate: async (currency: string): Promise<number> => {
-      console.log('[ATM Service] Fetching exchange rate for', currency)
-
-      try {
-        const rate = await lightningPub.getExchangeRate(currency)
-        console.log('[ATM Service] Exchange rate:', rate.satsPerUnit, 'sats/' + currency)
-        return rate.satsPerUnit
-      } catch (error) {
-        console.warn('[ATM Service] Failed to fetch rate, using fallback:', error)
-        // Fallback rate for development
-        return 2500 // sats per USD (~$40k BTC)
-      }
+      console.log('[ATM Service] Using fixed exchange rate for', currency)
+      // Fixed rate for development/testing
+      return 1000 // sats per USD (~$100k BTC)
     },
 
     /**

lamassu-next/apps/machine/src/stores/atm.ts

@@ -41,7 +41,7 @@ const mockServices: ATMServices = {
 
   getExchangeRate: async (currency) => {
     console.log('[Mock] Fetching exchange rate for', currency)
-    return 2500
+    return 1000 // 1000 sats per USD (~$100k BTC)
   },
 
   sendNostrReceipt: async (context) => {

lamassu-next/packages/state-machine/src/__tests__/machine.test.ts

@@ -75,7 +75,7 @@ describe('ATM State Machine', () => {
 
       const context = actor.getSnapshot().context
       expect(context.billsInserted).toEqual([20, 10])
-      expect(context.fiatAmount).toBe(30) // $30 in cents? No, as dollars
+      expect(context.fiatAmount).toBe(3000) // $30 in cents
     })
 
     it('should return to idle on CANCEL', async () => {

lamassu-next/packages/state-machine/src/machine.ts

@@ -145,7 +145,8 @@ export function createATMMachine(services: Partial<ATMServices> = {}) {
         },
         fiatAmount: ({ context, event }) => {
           if (event.type !== 'BILL_INSERTED') return context.fiatAmount
-          return context.fiatAmount + event.denomination
+          // denomination is in dollars, fiatAmount is in cents
+          return context.fiatAmount + event.denomination * 100
         },
       }),
       calculateSats: assign({