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>

versions.mk

@@ -1,10 +1,10 @@
 # Single source of truth for all platform versions (semver).
 # Bump with: make bump PLATFORM=<server|linux|macos|windows|bsd|android> PART=<major|minor|patch>
-VERSION_SERVER   := 0.12.0
-VERSION_LINUX    := 0.6.0
-VERSION_MACOS    := 0.6.0
-VERSION_WINDOWS  := 0.6.0
-VERSION_BSD      := 0.6.0
+VERSION_SERVER   := 0.12.1
+VERSION_LINUX    := 0.6.1
+VERSION_MACOS    := 0.6.1
+VERSION_WINDOWS  := 0.6.1
+VERSION_BSD      := 0.6.1
 VERSION_ANDROID  := 0.4.0
 # Monotonic Android versionCode, never decreases.
 ANDROID_VERSION_CODE := 4