fix(proxy): background ctx for already-started AddPeer notification

The earlier ctx fix covered the async runClientStartup path but missed
the synchronous branch: when a service is added to an already-started
client, AddPeer called NotifyStatus with the caller's request-scoped
ctx. A cancelled request/stream could drop the connected notification
to management. Use context.Background() here too, matching
notifyClientReady.

Extends TestNetBird_AddPeer_ExistingStartedClient_NotifiesStatus to
pass a pre-cancelled caller ctx and assert the notification still ran
on a non-cancelled context.

proxy/internal/roundtrip/netbird.go

@@ -213,7 +213,11 @@ func (n *NetBird) AddPeer(ctx context.Context, accountID types.AccountID, key Se
 		}).Debug("registered service with existing client")
 
 		if started && n.statusNotifier != nil {
-			if err := n.statusNotifier.NotifyStatus(ctx, accountID, serviceID, true); err != nil {
+			// Use a background context, not the caller's: the management
+			// connection notification must land even if the request /
+			// stream that triggered this registration is cancelled.
+			// Mirrors the async runClientStartup path.
+			if err := n.statusNotifier.NotifyStatus(context.Background(), accountID, serviceID, true); err != nil {
 				n.logger.WithFields(log.Fields{
 					"account_id":  accountID,
 					"service_key": key,

proxy/internal/roundtrip/netbird_test.go

@@ -299,8 +299,12 @@ func TestNetBird_AddPeer_ExistingStartedClient_NotifiesStatus(t *testing.T) {
 	nb.clients[accountID].started = true
 	nb.clientsMux.Unlock()
 
-	// Add second service — should notify immediately since client is already started.
+	// Add second service with an already-cancelled caller context —
-	err = nb.AddPeer(context.Background(), accountID, "domain2.test", "key-1", types.ServiceID("svc-2"))
+	// should notify immediately (client is started) AND the notification
+	// must not inherit the cancelled ctx.
+	cancelledCtx, cancel := context.WithCancel(context.Background())
+	cancel()
+	err = nb.AddPeer(cancelledCtx, accountID, "domain2.test", "key-1", types.ServiceID("svc-2"))
 	require.NoError(t, err)
 
 	calls := notifier.calls()
@@ -308,6 +312,9 @@ func TestNetBird_AddPeer_ExistingStartedClient_NotifiesStatus(t *testing.T) {
 	assert.Equal(t, accountID, calls[0].accountID)
 	assert.Equal(t, types.ServiceID("svc-2"), calls[0].serviceID)
 	assert.True(t, calls[0].connected)
+	require.NotNil(t, calls[0].ctx, "NotifyStatus must receive a context")
+	require.NoError(t, calls[0].ctx.Err(),
+		"already-started NotifyStatus must use a background ctx, not the cancelled caller ctx")
 }
 
 // TestNetBird_IdentityForIP_UnknownAccountReturnsFalse confirms that the