Tidy the Linux packages and tray after testing on Debian 13

Verified on Debian 13 arm64 with Cinnamon: the .deb installs, the tray
registers and renders its menu, and pull and push sync end to end.

- Packages ship 0755 directories whatever the builder's umask, name the
  native changelog changelog.gz, and override lintian for the static
  binary and the 0640 server config; prerm uses deb-systemd-invoke.
- The tray item is titled KeepOrg for StatusNotifierItem hosts.
- Event log lines omit empty fields.
- -reset-admin help no longer says to stop the server.

Client 0.6.1 (Linux, macOS, Windows, BSD), server 0.12.1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/client/mirror.go

@@ -152,7 +152,14 @@ func (m *Mirror) listen(ctx context.Context, wake func()) {
 	for ctx.Err() == nil {
 		err := m.api.Events(ctx, func(ev Event) {
 			backoff = time.Second
-			m.log.Printf("event %s %s v%d by %s", ev.Type, ev.Name, ev.Version, ev.By)
+			line := "event " + ev.Type
+			if ev.Name != "" {
+				line += fmt.Sprintf(" %s v%d", ev.Name, ev.Version)
+			}
+			if ev.By != "" {
+				line += " by " + ev.By
+			}
+			m.log.Print(line)
 			wake()
 		})
 		if ctx.Err() != nil {