feat(wallet): QR scan modal — camera + animated QR, wired into Home/Send/Receive

New WalletScanModal scans QR codes with the device camera (BarcodeDetector
with jsQR fallback) including animated/multi-frame QRs via qrloop, then
routes what it saw: BOLT11 invoices -> lightning pay (amount locked from
the invoice when present), bitcoin:/BIP21 URIs -> on-chain send, Cashu
tokens -> redeem, Fedimint invites -> join. Entry points: camera button on
the wallet card (far right), and a Scan button centered between the
Close/Send and Close/Receive buttons of both modals.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/components/SendBitcoinModal.vue

@@ -69,6 +69,12 @@
 
         <div class="flex gap-3">
           <button @click="close" class="flex-1 glass-button px-4 py-2 rounded-lg text-sm">{{ t('common.close') }}</button>
+          <button @click="$emit('scan')" class="flex-1 glass-button px-4 py-2 rounded-lg text-sm font-medium flex items-center justify-center gap-2">
+            <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 8V6a2 2 0 012-2h2M3 16v2a2 2 0 002 2h2m10-16h2a2 2 0 012 2v2m-4 12h2a2 2 0 002-2v-2M7 12h10" />
+            </svg>
+            Scan
+          </button>
           <button @click="send" :disabled="processing || (!amount && !isSweep)" class="flex-1 glass-button glass-button-warning px-4 py-2 rounded-lg text-sm font-medium disabled:opacity-50">
             {{ processing ? t('common.sending') : t('common.send') }}
           </button>
@@ -85,7 +91,7 @@ import BaseModal from '@/components/BaseModal.vue'
 const { t } = useI18n()
 
 const props = defineProps<{ show: boolean }>()
-const emit = defineEmits<{ close: []; sent: [] }>()
+const emit = defineEmits<{ close: []; sent: []; scan: [] }>()
 
 const sendMethod = ref<'auto' | 'lightning' | 'onchain' | 'ecash' | 'ark'>('auto')
 const amount = ref<number>(0)