fix(machine): maintenance beacon uses the pairing seed's relay (#70)

The maintenance-mode beacon resolved the relay from env only (config.relayUrl ||
VITE_RELAY_URL), so on a blank-.env seed-driven machine it was undefined and the
beacon was skipped — a paired ATM in maintenance never broadcast. It already
resolves the signer (which carries the transport); fall back to
resolved.transport.relays[0], mirroring lightning.ts's env → pairing precedence.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/machine/src/App.vue

@@ -103,11 +103,16 @@ onMounted(async () => {
     try {
       const { NostrClient, createSignedEvent } = await import('@bitSpire/nostr-client')
       const { resolveSigner } = await import('@/services/signer-resolver')
-      const relayUrl = config?.relayUrl || import.meta.env.VITE_RELAY_URL
       // Best-effort: resolve a signer (bunker resume / pairing, or dev nsec).
       // If the ATM isn't paired yet, skip the beacon rather than fail the screen.
       const resolved = await resolveSigner({ allowEphemeral: true }).catch(() => null)
       const signer = resolved?.signer ?? null
+      // Same env → pairing-seed precedence as lightning.ts: on a blank-.env
+      // seed-driven machine the relay comes from the pairing transport, not env.
+      const relayUrl =
+        config?.relayUrl ||
+        import.meta.env.VITE_RELAY_URL ||
+        resolved?.transport?.relays?.[0]
       if (signer && relayUrl) {
         const client = new NostrClient({ relays: [{ url: relayUrl }], signer })
         await client.connect()