[client] Add NAT-PMP/UPnP support (#5202)

client/internal/portforward/manager_js.go

@@ -0,0 +1,36 @@
+package portforward
+
+import (
+	"context"
+	"net"
+)
+
+// Mapping represents port mapping information.
+type Mapping struct {
+	Protocol     string
+	InternalPort uint16
+	ExternalPort uint16
+	ExternalIP   net.IP
+	NATType      string
+}
+
+// Manager is a stub for js/wasm builds where NAT-PMP/UPnP is not supported.
+type Manager struct{}
+
+// NewManager returns a stub manager for js/wasm builds.
+func NewManager() *Manager {
+	return &Manager{}
+}
+
+// Start is a no-op on js/wasm: NAT-PMP/UPnP is not available in browser environments.
+func (m *Manager) Start(context.Context, uint16) {
+	// no NAT traversal in wasm
+}
+
+// GracefullyStop is a no-op on js/wasm.
+func (m *Manager) GracefullyStop(context.Context) error { return nil }
+
+// GetMapping always returns nil on js/wasm.
+func (m *Manager) GetMapping() *Mapping {
+	return nil
+}