[client] Unify peer and route ACL filtering with multi-source rules (#6322)

* Unify peer and route ACL filtering with multi-source peer rules

* Remove partial userspace firewall mode and open foreign chains via a table-less allower

* Snapshot iptables rule maps before persisting state

* Scope userspace firewall wildcard source rules per address family

* Install nftables peer filter and mangle rules in a single transaction

* Share the iptables jump rule spec between install and cleanup

* Fix legacy ACL source wildcard and keep rollback tracking on delete failure

* Fix CI: recognize multi-value port set lookups in tests and correct PeerIP lint suppression

* Fall back to per-prefix filter rules when ipset is unavailable

* Annotate legacy PeerIP usages in ACL tests and fix import formatting

* Keep firewall rule bookkeeping in step with the kernel on replace and teardown

* Release the routing reference when the route manager shuts down

* Keep set references and rule tracking consistent when a routing rule fails

client/firewall/nftables/rule_linux.go

@@ -1,21 +1,26 @@
 package nftables
 
 import (
-	"net"
+	"net/netip"
 
 	"github.com/google/nftables"
+
+	"github.com/netbirdio/netbird/client/firewall/manager"
 )
 
-// Rule to handle management of rules
+// Rule wraps an installed filter rule (peer or route). Source set
+// membership is encoded in the rule's expressions; DeleteFilterRule
+// recovers the set name via findSets so the refcounter can drop the
+// right reference. mangleRule is set only for peer rules.
 type Rule struct {
 	nftRule    *nftables.Rule
 	mangleRule *nftables.Rule
-	nftSet     *nftables.Set
-	ruleID     string
-	ip         net.IP
+	// sources is the canonical source list this rule was created for.
+	sources []netip.Prefix
+	id      manager.RuleID
 }
 
-// GetRuleID returns the rule id
-func (r *Rule) ID() string {
-	return r.ruleID
+// ID returns the rule id
+func (r *Rule) ID() manager.RuleID {
+	return r.id
 }