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>

cmd/keeporgd/main.go

@@ -111,7 +111,7 @@ func main() {
 			"write a commented example config to this path and exit")
 		resetAdmin = flag.Bool("reset-admin", false,
 			"reset the built-in administrator's password, print a new one and "+
-				"exit; stop the server first")
+				"exit; a running server picks it up within seconds")
 	)
 	flag.Parse()