[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.

client/internal/peer/conn.go

@@ -26,7 +26,7 @@ import (
 	"github.com/netbirdio/netbird/client/internal/portforward"
 	"github.com/netbirdio/netbird/client/internal/rosenpass"
 	"github.com/netbirdio/netbird/client/internal/stdnet"
-	"github.com/netbirdio/netbird/client/netstate"
+	"github.com/netbirdio/netbird/client/netevents"
 	"github.com/netbirdio/netbird/route"
 	relayClient "github.com/netbirdio/netbird/shared/relay/client"
 )
@@ -97,7 +97,7 @@ type ConnConfig struct {
 
 	// NetworkState gates the reconnection guard on OS-reported network
 	// availability; nil disables gating.
-	NetworkState *netstate.State
+	NetworkState *netevents.Manager
 }
 
 type Conn struct {

client/internal/peer/guard/guard.go

@@ -6,8 +6,6 @@ import (
 
 	"github.com/cenkalti/backoff/v4"
 	log "github.com/sirupsen/logrus"
-
-	"github.com/netbirdio/netbird/client/netstate"
 )
 
 // ConnStatus represents the connection state as seen by the guard.
@@ -24,6 +22,12 @@ const (
 
 type connStatusFunc func() ConnStatus
 
+// NetworkWatcher is the availability view the guard gates reconnects on.
+type NetworkWatcher interface {
+	IsOnline() bool
+	Changed() <-chan struct{}
+}
+
 // Guard is responsible for the reconnection logic.
 // It will trigger to send an offer to the peer then has connection issues.
 // Watch these events:
@@ -39,14 +43,14 @@ type Guard struct {
 	srWatcher           *SRWatcher
 	// netState gates reconnect attempts on OS-reported network availability;
 	// nil disables gating.
-	netState                *netstate.State
+	netState                NetworkWatcher
 	relayedConnDisconnected chan struct{}
 	iCEConnDisconnected     chan struct{}
 }
 
 // NewGuard creates a reconnection guard for a peer connection. A nil netState
 // disables network availability gating.
-func NewGuard(log *log.Entry, isConnectedFn connStatusFunc, timeout time.Duration, srWatcher *SRWatcher, netState *netstate.State) *Guard {
+func NewGuard(log *log.Entry, isConnectedFn connStatusFunc, timeout time.Duration, srWatcher *SRWatcher, netState NetworkWatcher) *Guard {
 	return &Guard{
 		log:                     log,
 		isConnectedOnAllWay:     isConnectedFn,
@@ -104,14 +108,17 @@ func (g *Guard) reconnectLoopWithRetry(ctx context.Context, callback func()) {
 	iceState := &iceRetryState{log: g.log}
 	defer iceState.reset()
 
-	netChanged := g.netState.Changed()
+	var netChanged <-chan struct{}
+	if g.netState != nil {
+		netChanged = g.netState.Changed()
+	}
 
 	for {
 		select {
 		case <-tickerChannel:
 			// skip attempts while the OS reports no usable network; the
 			// netChanged case below resumes the loop once it returns
-			if !g.netState.IsOnline() {
+			if g.netState != nil && !g.netState.IsOnline() {
 				continue
 			}
 			switch g.isConnectedOnAllWay() {

client/internal/peer/guard/guard_netstate_test.go

@@ -9,7 +9,7 @@ import (
 	log "github.com/sirupsen/logrus"
 
 	"github.com/netbirdio/netbird/client/internal/peer/ice"
-	"github.com/netbirdio/netbird/client/netstate"
+	"github.com/netbirdio/netbird/client/netevents/netstate"
 )
 
 // newTestGuardWithNetState builds a guard with a realistic MaxInterval: the