feat: machine Reset endpoint with asynchronous resource and data cleanup

internal/machine/firewall/iptables_darwin.go

@@ -6,3 +6,8 @@ import "fmt"
 func ConfigureIptablesChains() error {
 	return fmt.Errorf("not supported on Darwin")
 }
+
+// CleanupIptablesChains is a stub for Darwin.
+func CleanupIptablesChains() error {
+	return fmt.Errorf("not supported on Darwin")
+}

internal/machine/firewall/iptables_linux.go

@@ -16,7 +16,7 @@ const (
 
 // ConfigureIptablesChains sets up custom iptables chains and initial firewall rules for Uncloud networking.
 func ConfigureIptablesChains() error {
-	// Ensure iptables UNCLOUD-INPUT chain with a RETURN rule exists. All existing rules are flushed.
+	// Ensure iptables UNCLOUD-INPUT chain exists. All existing rules are flushed.
 	ipt := iptables.GetIptable(iptables.IPv4)
 	if _, err := ipt.NewChain(UncloudInputChain, iptables.Filter); err != nil {
 		return fmt.Errorf("create iptables chain '%s': %w", UncloudInputChain, err)
@@ -24,9 +24,6 @@ func ConfigureIptablesChains() error {
 	if err := ipt.RawCombinedOutput("-t", string(iptables.Filter), "-F", UncloudInputChain); err != nil {
 		return fmt.Errorf("flush iptables chain '%s': %w", UncloudInputChain, err)
 	}
-	if err := ipt.AddReturnRule(UncloudInputChain); err != nil {
-		return fmt.Errorf("add the RETURN rule for iptables chain '%s': %w", UncloudInputChain, err)
-	}
 
 	// Ensure the main iptables INPUT chain has a jump rule to the UNCLOUD-INPUT chain before any DROP/REJECT rules.
 	jumpRule := []string{"-m", "comment", "--comment", "Uncloud-managed", "-j", UncloudInputChain}