[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.

proxy/internal/restrict/restrict_test.go

@@ -514,6 +514,34 @@ func TestFilter_CrowdSec_Observe_NilChecker(t *testing.T) {
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
 }
 
+func TestFilter_CheckCIDR_AllowsWithoutCountryOrCrowdSec(t *testing.T) {
+	cs := &mockCrowdSec{ready: true, decisions: map[string]*CrowdSecDecision{
+		"100.64.5.6": {Type: DecisionBan},
+	}}
+	f := ParseFilter(FilterConfig{
+		AllowedCIDRs:     []string{"100.64.0.0/10"},
+		AllowedCountries: []string{"US"},
+		CrowdSec:         cs,
+		CrowdSecMode:     CrowdSecEnforce,
+	})
+
+	// CheckCIDR skips country + CrowdSec evaluation: an address inside
+	// the allowed CIDR passes even when it would be denied by CrowdSec
+	// or by the country allowlist (CGNAT addresses have no geo data).
+	assert.Equal(t, Allow, f.CheckCIDR(netip.MustParseAddr("100.64.5.6")),
+		"CheckCIDR must not run CrowdSec lookups on overlay traffic")
+
+	// CIDR denials still fire.
+	assert.Equal(t, DenyCIDR, f.CheckCIDR(netip.MustParseAddr("198.51.100.1")),
+		"CheckCIDR must still reject addresses outside the allow list")
+}
+
+func TestFilter_CheckCIDR_NilFilter(t *testing.T) {
+	var f *Filter
+	assert.Equal(t, Allow, f.CheckCIDR(netip.MustParseAddr("100.64.5.6")),
+		"CheckCIDR on a nil filter must allow")
+}
+
 func TestFilter_HasRestrictions_CrowdSec(t *testing.T) {
 	cs := &mockCrowdSec{ready: true}
 	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecEnforce})