[management, client, proxy] add expose NetBird-only services over tunnel peers (#6226)

Adds a new "private" service mode for the reverse proxy: services reachable exclusively over the embedded WireGuard tunnel, gated by per-peer group membership instead of operator auth schemes.

Wire contract
- ProxyMapping.private (field 13): the proxy MUST call ValidateTunnelPeer and fail closed; operator schemes are bypassed.
- ProxyCapabilities.private (4) + supports_private_service (5): capability gate. Management never streams private mappings to proxies that don't claim the capability; the broadcast path applies the same filter via filterMappingsForProxy.
- ValidateTunnelPeer RPC: resolves an inbound tunnel IP to a peer, checks the peer's groups against service.AccessGroups, and mints a session JWT on success. checkPeerGroupAccess fails closed when a private service has empty AccessGroups.
- ValidateSession/ValidateTunnelPeer responses now carry peer_group_ids + peer_group_names so the proxy can authorise policy-aware middlewares without an extra management round-trip.
- ProxyInboundListener + SendStatusUpdate.inbound_listener: per-account inbound listener state surfaced to dashboards.
- PathTargetOptions.direct_upstream (11): bypass the embedded NetBird client and dial the target via the proxy host's network stack for upstreams reachable without WireGuard.

Data model
- Service.Private (bool) + Service.AccessGroups ([]string, JSON- serialised). Validate() rejects bearer auth on private services. Copy() deep-copies AccessGroups. pgx getServices loads the columns.
- DomainConfig.Private threaded into the proxy auth middleware. Request handler routes private services through forwardWithTunnelPeer and returns 403 on validation failure.
- Account-level SynthesizePrivateServiceZones (synthetic DNS) and injectPrivateServicePolicies (synthetic ACL) gate on len(svc.AccessGroups) > 0.

Proxy
- /netbird proxy --private (embedded mode) flag; Config.Private in proxy/lifecycle.go.
- Per-account inbound listener (proxy/inbound.go) binding HTTP/HTTPS on the embedded NetBird client's WireGuard tunnel netstack.
- proxy/internal/auth/tunnel_cache: ValidateTunnelPeer response cache with single-flight de-duplication and per-account eviction.
- Local peerstore short-circuit: when the inbound IP isn't in the account roster, deny fast without an RPC.
- proxy/server.go reports SupportsPrivateService=true and redacts the full ProxyMapping JSON from info logs (auth_token + header-auth hashed values now only at debug level).

Identity forwarding
- ValidateSessionJWT returns user_id, email, method, groups, group_names. sessionkey.Claims carries Email + Groups + GroupNames so the proxy can stamp identity onto upstream requests without an extra management round-trip on every cookie-bearing request.
- CapturedData carries userEmail / userGroups / userGroupNames; the proxy stamps X-NetBird-User and X-NetBird-Groups on r.Out from the authenticated identity (strips client-supplied values first to prevent spoofing).
- AccessLog.UserGroups: access-log enrichment captures the user's group memberships at write time so the dashboard can render group context without reverse-resolving stale memberships.

OpenAPI/dashboard surface
- ReverseProxyService gains private + access_groups; ReverseProxyCluster gains private + supports_private. ReverseProxyTarget target_type enum gains "cluster". ServiceTargetOptions gains direct_upstream. ProxyAccessLog gains user_groups.

management/server/store/sql_store.go

@@ -1090,6 +1090,38 @@ func (s *SqlStore) GetCustomDomainsCounts(ctx context.Context) (int64, int64, er
 	return total, validated, nil
 }
 
+// GetProxyMetrics aggregates per-cluster + per-proxy counts for the
+// self-hosted telemetry payload. Single round-trip via conditional
+// aggregations so a large proxies table doesn't fan out into multiple
+// queries.
+func (s *SqlStore) GetProxyMetrics(ctx context.Context) (ProxyMetrics, error) {
+	var m ProxyMetrics
+	activeCutoff := time.Now().Add(-proxyActiveThreshold)
+
+	// COUNT(DISTINCT ... CASE WHEN ...) is portable across sqlite/postgres
+	// (MySQL too) and keeps the round-trip to one. proxy.StatusConnected
+	// is the same string the cluster-capability queries use; the active
+	// window matches the cluster-capability semantics (only proxies
+	// heartbeating within ~2 * heartbeat interval count as connected).
+	row := s.db.WithContext(ctx).
+		Model(&proxy.Proxy{}).
+		Select(
+			"COUNT(DISTINCT cluster_address) AS clusters, "+
+				"COUNT(DISTINCT CASE WHEN account_id IS NOT NULL THEN cluster_address END) AS clusters_byop, "+
+				"COUNT(DISTINCT CASE WHEN private = ? THEN cluster_address END) AS clusters_private, "+
+				"COUNT(*) AS proxies, "+
+				"COUNT(CASE WHEN status = ? AND last_seen > ? THEN 1 END) AS proxies_connected",
+			true,
+			proxy.StatusConnected,
+			activeCutoff,
+		).
+		Row()
+	if err := row.Scan(&m.Clusters, &m.ClustersBYOP, &m.ClustersPrivate, &m.Proxies, &m.ProxiesConnected); err != nil {
+		return ProxyMetrics{}, fmt.Errorf("scan proxy metrics: %w", err)
+	}
+	return m, nil
+}
+
 func (s *SqlStore) GetAllAccounts(ctx context.Context) (all []*types.Account) {
 	var accounts []types.Account
 	result := s.db.Find(&accounts)
@@ -2178,7 +2210,8 @@ func (s *SqlStore) getServices(ctx context.Context, accountID string) ([]*rpserv
 	const serviceQuery = `SELECT id, account_id, name, domain, enabled, auth,
 		meta_created_at, meta_certificate_issued_at, meta_status, proxy_cluster,
 		pass_host_header, rewrite_redirects, session_private_key, session_public_key,
-		mode, listen_port, port_auto_assigned, source, source_peer, terminated
+		mode, listen_port, port_auto_assigned, source, source_peer, terminated,
+		private, access_groups
 		FROM services WHERE account_id = $1`
 
 	const targetsQuery = `SELECT id, account_id, service_id, path, host, port, protocol,
@@ -2193,10 +2226,11 @@ func (s *SqlStore) getServices(ctx context.Context, accountID string) ([]*rpserv
 	services, err := pgx.CollectRows(serviceRows, func(row pgx.CollectableRow) (*rpservice.Service, error) {
 		var s rpservice.Service
 		var auth []byte
+		var accessGroups []byte
 		var createdAt, certIssuedAt sql.NullTime
 		var status, proxyCluster, sessionPrivateKey, sessionPublicKey sql.NullString
 		var mode, source, sourcePeer sql.NullString
-		var terminated, portAutoAssigned sql.NullBool
+		var terminated, portAutoAssigned, private sql.NullBool
 		var listenPort sql.NullInt64
 		err := row.Scan(
 			&s.ID,
@@ -2219,6 +2253,8 @@ func (s *SqlStore) getServices(ctx context.Context, accountID string) ([]*rpserv
 			&source,
 			&sourcePeer,
 			&terminated,
+			&private,
+			&accessGroups,
 		)
 		if err != nil {
 			return nil, err
@@ -2230,6 +2266,16 @@ func (s *SqlStore) getServices(ctx context.Context, accountID string) ([]*rpserv
 			}
 		}
 
+		if len(accessGroups) > 0 {
+			if err := json.Unmarshal(accessGroups, &s.AccessGroups); err != nil {
+				return nil, fmt.Errorf("unmarshal access_groups: %w", err)
+			}
+		}
+
+		if private.Valid {
+			s.Private = private.Bool
+		}
+
 		s.Meta = rpservice.Meta{}
 		if createdAt.Valid {
 			s.Meta.CreatedAt = createdAt.Time
@@ -5826,6 +5872,7 @@ var validCapabilityColumns = map[string]struct{}{
 	"supports_custom_ports": {},
 	"require_subdomain":     {},
 	"supports_crowdsec":     {},
+	"private":               {},
 }
 
 // GetClusterSupportsCustomPorts returns whether any active proxy in the cluster
@@ -5840,6 +5887,12 @@ func (s *SqlStore) GetClusterRequireSubdomain(ctx context.Context, clusterAddr s
 	return s.getClusterCapability(ctx, clusterAddr, "require_subdomain")
 }
 
+// GetClusterSupportsPrivate reports whether any active proxy in the cluster
+// has the private capability (nil = unreported).
+func (s *SqlStore) GetClusterSupportsPrivate(ctx context.Context, clusterAddr string) *bool {
+	return s.getClusterCapability(ctx, clusterAddr, "private")
+}
+
 // GetClusterSupportsCrowdSec returns whether all active proxies in the cluster
 // have CrowdSec configured. Returns nil when no proxy reported the capability.
 // Unlike other capabilities that use ANY-true (for rolling upgrades), CrowdSec