fix: use fiat code from env in command queue poller

The command poller hardcoded 'GTQ' as the currency for manual dispense
transactions. Now reads VITE_LAMASSU_FIAT_CODE from env, defaulting
to 'USD'.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/machine/electron/main.ts

@@ -396,6 +396,7 @@ function startCommandPoller(): void {
         const result = await halInstance.dispenseCash(parsed.bills)
         const txid = `manual-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`
         const totalFiatCents = parsed.bills.reduce((s, b) => s + b.denomination * b.count * 100, 0)
+        const fiatCode = process.env.VITE_LAMASSU_FIAT_CODE || 'USD'
 
         recordTransaction({
           txid,
@@ -406,7 +407,7 @@ function startCommandPoller(): void {
           feeSats: 0,
           feePercent: 0,
           exchangeRate: 0,
-          currency: 'GTQ',
+          currency: fiatCode,
           bills: parsed.bills,
           cassettes: result.cassettes,
           error: result.error,