feat: reload also scrubs expired leases from lease file before reloading dnsmasq

server.go

@@ -197,6 +197,11 @@ func unpinLease(mac string) error {
 
 // reloadDnsmasq runs the reload command (e.g. sudo systemctl reload dnsmasq).
 func reloadDnsmasq() error {
+	// Scrub expired leases before reloading so the UI stays clean.
+	if err := cleanLeaseFile(); err != nil {
+		log.Printf("WARNING: failed to clean lease file: %v", err)
+		// Continue — reload is still useful even if cleaning fails.
+	}
 	cmd := exec.Command(reloadCmd, reloadArgs...)
 	output, err := cmd.CombinedOutput()
 	if err != nil {
@@ -205,6 +210,52 @@ func reloadDnsmasq() error {
 	return nil
 }
 
+// cleanLeaseFile reads the lease file, removes expired entries, writes back atomically.
+func cleanLeaseFile() error {
+	leases, err := parseLeases()
+	if err != nil {
+		return err
+	}
+
+	now := time.Now()
+	var kept []string
+	for _, l := range leases {
+		if l.Expiry.After(now) {
+			kept = append(kept, fmt.Sprintf("%d %s %s %s %s",
+				l.Expiry.Unix(), l.MAC, l.IP, l.Hostname, l.ClientID))
+		}
+	}
+
+	// If nothing changed, skip the write.
+	if len(kept) == len(leases) {
+		return nil
+	}
+
+	tmpFile := leasesFile + ".tmp"
+	f, err := os.Create(tmpFile)
+	if err != nil {
+		return fmt.Errorf("create temp lease file: %w", err)
+	}
+	writeErr := func() error {
+		defer f.Close()
+		for _, line := range kept {
+			if _, err := fmt.Fprintln(f, line); err != nil {
+				return err
+			}
+		}
+		return nil
+	}()
+	if writeErr != nil {
+		os.Remove(tmpFile)
+		return writeErr
+	}
+	if err := os.Rename(tmpFile, leasesFile); err != nil {
+		os.Remove(tmpFile)
+		return fmt.Errorf("rename lease file: %w", err)
+	}
+	return nil
+}
+
 // getAllLeases returns merged active (non-expired) and pinned lease info.
 func getAllLeases() ([]LeaseEntry, error) {
 	activeLeases, err := parseLeases()