[client] Sweep connections on network loss via a shared netevents manager

Losing the last network only flipped the availability state: the dead
management, signal and relay sockets stayed silently connected until their
own timeouts, so the client kept reporting Connected with no network at all.

Introduce client/netevents with a Manager that ties the availability state,
the connection sweeper and the status recorder together, and move the
netstate and netsweep packages under it (netsweep renamed to sweep).
SetNetworkAvailable(false) now also sweeps the registered connections so
their owners redial and the listener reaches the NoNetwork state.

The Android and iOS bindings own a Manager instance and inject it through
the constructors; consumers hold the concrete *Manager whose nil zero value
reports always-online and never sweeps, with interfaces kept only as
parameter contracts. The relay guard settle wait moved into the Manager as
WaitSettled, removing the netevents import from the relay package.

shared/management/client/grpc.go

@@ -21,8 +21,7 @@ import (
 	"google.golang.org/grpc/connectivity"
 
 	nbgrpc "github.com/netbirdio/netbird/client/grpc"
-	"github.com/netbirdio/netbird/client/netstate"
-	"github.com/netbirdio/netbird/client/netsweep"
+	"github.com/netbirdio/netbird/client/netevents"
 	"github.com/netbirdio/netbird/client/system"
 	"github.com/netbirdio/netbird/encryption"
 	"github.com/netbirdio/netbird/shared/management/domain"
@@ -64,12 +63,9 @@ type GrpcClient struct {
 	connStateCallbackLock sync.RWMutex
 	serverURL             string
 
-	// netState gates the stream retry loop on OS-reported network
-	// availability; nil (the default) disables gating.
-	netState *netstate.State
-
-	// sweeper cuts the transport connections on network change; nil disables it.
-	sweeper *netsweep.Sweeper
+	// netEvents gates the stream retry loop on OS-reported network
+	// availability and sweeps the transport on network change.
+	netEvents *netevents.Manager
 
 	// syncStreamErr holds the last Sync stream error, or nil while the stream
 	// is established and healthy. GetServerKey succeeds even when the peer
@@ -123,15 +119,9 @@ func MaxRecvMsgSize() int {
 // Option configures optional GrpcClient behavior.
 type Option func(*GrpcClient)
 
-// WithNetworkState injects the OS network availability state that gates the
-// stream retry loop; without it gating is disabled.
-func WithNetworkState(netState *netstate.State) Option {
-	return func(c *GrpcClient) { c.netState = netState }
-}
-
-// WithSweeper injects the network change sweeper.
-func WithSweeper(sweeper *netsweep.Sweeper) Option {
-	return func(c *GrpcClient) { c.sweeper = sweeper }
+// WithNetEvents injects the OS network event handling.
+func WithNetEvents(events *netevents.Manager) Option {
+	return func(c *GrpcClient) { c.netEvents = events }
 }
 
 // NewClient creates a new client to Management service
@@ -152,9 +142,7 @@ func NewClient(ctx context.Context, addr string, ourPrivateKey wgtypes.Key, tlsE
 		extraOpts = append(extraOpts, grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(maxSize)))
 		log.Infof("management gRPC max receive message size set to %d bytes", maxSize)
 	}
-	if c.sweeper != nil {
-		extraOpts = append(extraOpts, nbgrpc.WithSweeper(c.sweeper))
-	}
+	extraOpts = append(extraOpts, nbgrpc.WithSweeper(c.netEvents))
 
 	var conn *grpc.ClientConn
 	operation := func() error {
@@ -235,12 +223,12 @@ func (c *GrpcClient) withMgmtStream(
 	ctx context.Context,
 	handler func(ctx context.Context, serverPubKey wgtypes.Key, backOff backoff.BackOff) error,
 ) error {
-	backOff := c.sweeper.QuickRetryBackoff(ctx, defaultBackoff(ctx), c.netState)
+	backOff := c.netEvents.QuickRetryBackoff(ctx, defaultBackoff(ctx))
 	operation := func() error {
 		// suspend reconnect attempts while the OS reports no usable network.
 		// Wait only errors on a cancelled context, which means shutdown, so
 		// stop the loop without reporting a failure.
-		if waited, err := c.netState.Wait(ctx); err != nil {
+		if waited, err := c.netEvents.Wait(ctx); err != nil {
 			log.Debugf("management connection context has been canceled while offline, this usually indicates shutdown")
 			return nil //nolint:nilerr // a cancelled context means shutdown, not a retryable failure
 		} else if waited {
@@ -273,7 +261,7 @@ func (c *GrpcClient) withMgmtStream(
 		return handler(ctx, *serverPubKey, backOff)
 	}
 
-	err := nbgrpc.Retry(ctx, operation, backOff, c.netState)
+	err := nbgrpc.Retry(ctx, operation, backOff, c.netEvents)
 	if err != nil {
 		log.Warnf("exiting the Management service connection retry loop due to the unrecoverable error: %s", err)
 	}