fix(machine): UI polish — fiat rate display, 15s receipt with QR, remove CLINK

- Show exchange rate as fiat/BTC (e.g. Q615,000/BTC) instead of sats/fiat
- Show USD/BTC rate when currency != USD
- Complete screen stays 15s (was 3s) with txid QR code for receipt photo
- Add "Done" button for manual dismiss on complete screen
- Remove CLINK ndebit UI (mode selector, pubkey entry) pending k1 fix (#23)
- Remove askForReceipt/sendingReceipt screens (npub scan not active, #36)
- Remove negative sign on commission display
- Set timezone to America/Guatemala

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

packages/state-machine/src/machine.ts

@@ -379,7 +379,7 @@ export function createATMMachine(
     },
     delays: {
       TIMEOUT_MS: 300000, // 5 minutes
-      COMPLETE_DELAY: 3000,
+      COMPLETE_DELAY: 15000,
     },
   }).createMachine({
     id: 'atm',
@@ -482,7 +482,7 @@ export function createATMMachine(
             },
             on: {
               PAYMENT_RECEIVED: {
-                target: 'askForReceipt',
+                target: 'complete',
                 actions: 'setPaymentReceived',
               },
               PAYMENT_FAILED: {
@@ -523,6 +523,9 @@ export function createATMMachine(
             after: {
               COMPLETE_DELAY: '#atm.idle',
             },
+            on: {
+              CANCEL: '#atm.idle',
+            },
           },
           error: {
             on: {
@@ -653,8 +656,8 @@ export function createATMMachine(
           },
           waitingForCashTaken: {
             on: {
-              CASH_DISPENSED: 'askForReceipt',
-              TIMEOUT: 'askForReceipt', // Assume taken
+              CASH_DISPENSED: 'complete',
+              TIMEOUT: 'complete', // Assume taken
             },
           },
           askForReceipt: {
@@ -680,6 +683,9 @@ export function createATMMachine(
             after: {
               COMPLETE_DELAY: '#atm.idle',
             },
+            on: {
+              CANCEL: '#atm.idle',
+            },
           },
           dispenseError: {
             // Critical error - payment received but cash not dispensed