修复局域网连接问题

backend/internal/service/device_service_test.go

@@ -56,3 +56,60 @@ func TestRegisterReusesKnownDeviceOnlyWithValidToken(t *testing.T) {
 		t.Fatal("expected rotated device token to validate")
 	}
 }
+
+func TestListCandidatesOnlyReturnsSameNetworkDevices(t *testing.T) {
+	memStore := store.NewMemoryStore(model.RuntimeConfig{})
+	deviceService := NewDeviceService(memStore, nil, nil)
+
+	current, _ := deviceService.Register(RegisterDeviceInput{
+		DeviceID:        "current",
+		Name:            "Current",
+		Type:            "desktop",
+		NetworkGroupKey: "192.168.1.10",
+	}, "ua/1.0", "")
+
+	sameNetwork, _ := deviceService.Register(RegisterDeviceInput{
+		DeviceID:        "same-network",
+		Name:            "Same Network",
+		Type:            "phone",
+		NetworkGroupKey: "192.168.1.10",
+	}, "ua/1.0", "")
+
+	_, _ = deviceService.Register(RegisterDeviceInput{
+		DeviceID:        "other-network",
+		Name:            "Other Network",
+		Type:            "phone",
+		NetworkGroupKey: "10.0.0.5",
+	}, "ua/1.0", "")
+
+	candidates := deviceService.ListCandidates(current.ID)
+	if len(candidates) != 1 {
+		t.Fatalf("expected 1 same-network candidate, got %d", len(candidates))
+	}
+	if candidates[0].ID != sameNetwork.ID {
+		t.Fatalf("expected candidate %q, got %q", sameNetwork.ID, candidates[0].ID)
+	}
+}
+
+func TestListCandidatesReturnsEmptyWithoutNetworkGroupKey(t *testing.T) {
+	memStore := store.NewMemoryStore(model.RuntimeConfig{})
+	deviceService := NewDeviceService(memStore, nil, nil)
+
+	current, _ := deviceService.Register(RegisterDeviceInput{
+		DeviceID: "current",
+		Name:     "Current",
+		Type:     "desktop",
+	}, "ua/1.0", "")
+
+	_, _ = deviceService.Register(RegisterDeviceInput{
+		DeviceID:        "same-network",
+		Name:            "Same Network",
+		Type:            "phone",
+		NetworkGroupKey: "192.168.1.10",
+	}, "ua/1.0", "")
+
+	candidates := deviceService.ListCandidates(current.ID)
+	if len(candidates) != 0 {
+		t.Fatalf("expected no candidates without a local network group key, got %d", len(candidates))
+	}
+}