fix: NWC payment timeout/error now rejects properly (BUG-F4)

- Timeout and WebSocket errors reject with proper Error objects
- Caller catches and falls through to poll-based confirmation
- Preimage undefined check prevents calling confirm with no preimage

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

frontend/src/composables/useWallet.ts

@@ -173,16 +173,22 @@ export function useWallet() {
       }
       if (nwcUrl && nwcValid) {
         paymentStatus.value = 'paying'
-        const preimage = await payViaNWC(nwcUrl, bolt11)
-
-        // Tell server payment is confirmed (skip lookup_invoice polling)
-        await authFetch(`/api/payments/confirm/${paymentId}`, {
-          method: 'POST',
-          headers: { 'Content-Type': 'application/json' },
-          body: JSON.stringify({ preimage, pubkey: pubkey.value }),
-        })
-        paymentStatus.value = 'confirmed'
-        return paymentId
+        try {
+          const preimage = await payViaNWC(nwcUrl, bolt11)
+          if (preimage) {
+            await authFetch(`/api/payments/confirm/${paymentId}`, {
+              method: 'POST',
+              headers: { 'Content-Type': 'application/json' },
+              body: JSON.stringify({ preimage, pubkey: pubkey.value }),
+            })
+            paymentStatus.value = 'confirmed'
+            return paymentId
+          }
+        } catch (err) {
+          console.warn('[Wallet] NWC payment failed, falling back to polling:', err)
+        }
+        // NWC failed or returned no preimage — fall through to polling
+        paymentStatus.value = 'pending'
       }
 
       // No NWC — poll for confirmation (manual payment / QR code flow)
@@ -268,7 +274,7 @@ async function payViaNWC(nwcUrl: string, bolt11: string): Promise<string | undef
     const ws = new WebSocket(nwc.relay)
     const timeout = setTimeout(() => {
       ws.close()
-      resolve(undefined)
+      reject(new Error('NWC payment timed out'))
     }, 30_000)
 
     ws.onopen = () => {
@@ -309,7 +315,7 @@ async function payViaNWC(nwcUrl: string, bolt11: string): Promise<string | undef
 
     ws.onerror = () => {
       clearTimeout(timeout)
-      resolve(undefined)
+      reject(new Error('NWC WebSocket error'))
     }
   })
 }