[management] Fence peer status updates with a session token (#6193)

* [management] Fence peer status updates with a session token

The connect/disconnect path used a best-effort LastSeen-after-streamStart
comparison to decide whether a status update should land. Under contention
— a re-sync arriving while the previous stream's disconnect was still in
flight, or two management replicas seeing the same peer at once — the
check was a read-then-decide-then-write window: any UPDATE in between
caused the wrong row to be written. The Go-side time.Now() that fed the
comparison also drifted under lock contention, since it was captured
seconds before the write actually committed.

Replace it with an integer-nanosecond fencing token stored alongside the
status. Every gRPC sync stream uses its open time (UnixNano) as its token.
Connects only land when the incoming token is strictly greater than the
stored one; disconnects only land when the incoming token equals the
stored one (i.e. we're the stream that owns the current session). Both
are single optimistic-locked UPDATEs — no read-then-write, no transaction
wrapper.

LastSeen is now written by the database itself (CURRENT_TIMESTAMP). The
caller never supplies it, so the value always reflects the real moment
of the UPDATE rather than the moment the caller queued the work — which
was already off by minutes under heavy lock contention.

Side effects (geo lookup, peer-login-expiration scheduling, network-map
fan-out) are explicitly documented as running after the fence UPDATE
commits, never inside it. Geo also skips the update when realIP equals
the stored ConnectionIP, dropping a redundant SavePeerLocation call on
same-IP reconnects.

Tests cover the three semantic cases (matched disconnect lands, stale
disconnect dropped, stale connect dropped) plus a 16-goroutine race test
that asserts the highest token always wins.

* [management] Add SessionStartedAt to peer status updates

Stored `SessionStartedAt` for fencing token propagation across goroutines and updated database queries/functions to handle the new field. Removed outdated geolocation handling logic and adjusted tests for concurrency safety.

* Rename `peer_status_required_approval` to `peer_status_requires_approval` in SQL store fields

management/server/mock_server/account_mock.go

@@ -38,7 +38,8 @@ type MockAccountManager struct {
 	GetUserFromUserAuthFunc               func(ctx context.Context, userAuth auth.UserAuth) (*types.User, error)
 	ListUsersFunc                         func(ctx context.Context, accountID string) ([]*types.User, error)
 	GetPeersFunc                          func(ctx context.Context, accountID, userID, nameFilter, ipFilter string) ([]*nbpeer.Peer, error)
-	MarkPeerConnectedFunc                 func(ctx context.Context, peerKey string, connected bool, realIP net.IP, syncTime time.Time) error
+	MarkPeerConnectedFunc                 func(ctx context.Context, peerKey string, realIP net.IP, accountID string, sessionStartedAt int64) error
+	MarkPeerDisconnectedFunc              func(ctx context.Context, peerKey string, accountID string, sessionStartedAt int64) error
 	SyncAndMarkPeerFunc                   func(ctx context.Context, accountID string, peerPubKey string, meta nbpeer.PeerSystemMeta, realIP net.IP, syncTime time.Time) (*nbpeer.Peer, *types.NetworkMap, []*posture.Checks, int64, error)
 	DeletePeerFunc                        func(ctx context.Context, accountID, peerKey, userID string) error
 	GetNetworkMapFunc                     func(ctx context.Context, peerKey string) (*types.NetworkMap, error)
@@ -227,7 +228,14 @@ func (am *MockAccountManager) SyncAndMarkPeer(ctx context.Context, accountID str
 	return nil, nil, nil, 0, status.Errorf(codes.Unimplemented, "method MarkPeerConnected is not implemented")
 }
 
-func (am *MockAccountManager) OnPeerDisconnected(_ context.Context, accountID string, peerPubKey string, streamStartTime time.Time) error {
+func (am *MockAccountManager) OnPeerDisconnected(ctx context.Context, accountID string, peerPubKey string, streamStartTime time.Time) error {
+	// Mirror DefaultAccountManager.OnPeerDisconnected: drive the fencing
+	// hook so tests that inject MarkPeerDisconnectedFunc actually observe
+	// disconnect events. Falls through to nil when no hook is set, which
+	// is the original behaviour.
+	if am.MarkPeerDisconnectedFunc != nil {
+		return am.MarkPeerDisconnectedFunc(ctx, peerPubKey, accountID, streamStartTime.UnixNano())
+	}
 	return nil
 }
 
@@ -328,13 +336,21 @@ func (am *MockAccountManager) GetAccountIDByUserID(ctx context.Context, userAuth
 }
 
 // MarkPeerConnected mock implementation of MarkPeerConnected from server.AccountManager interface
-func (am *MockAccountManager) MarkPeerConnected(ctx context.Context, peerKey string, connected bool, realIP net.IP, accountID string, syncTime time.Time) error {
+func (am *MockAccountManager) MarkPeerConnected(ctx context.Context, peerKey string, realIP net.IP, accountID string, sessionStartedAt int64) error {
 	if am.MarkPeerConnectedFunc != nil {
-		return am.MarkPeerConnectedFunc(ctx, peerKey, connected, realIP, syncTime)
+		return am.MarkPeerConnectedFunc(ctx, peerKey, realIP, accountID, sessionStartedAt)
 	}
 	return status.Errorf(codes.Unimplemented, "method MarkPeerConnected is not implemented")
 }
 
+// MarkPeerDisconnected mock implementation of MarkPeerDisconnected from server.AccountManager interface
+func (am *MockAccountManager) MarkPeerDisconnected(ctx context.Context, peerKey string, accountID string, sessionStartedAt int64) error {
+	if am.MarkPeerDisconnectedFunc != nil {
+		return am.MarkPeerDisconnectedFunc(ctx, peerKey, accountID, sessionStartedAt)
+	}
+	return status.Errorf(codes.Unimplemented, "method MarkPeerDisconnected is not implemented")
+}
+
 // DeleteAccount mock implementation of DeleteAccount from server.AccountManager interface
 func (am *MockAccountManager) DeleteAccount(ctx context.Context, accountID, userID string) error {
 	if am.DeleteAccountFunc != nil {