Modernize the Windows installer, tray and runtime control; fix lifecycle bugs.

Installer: dynamic light/dark Win11 style, new brand wizard images, auto
language, exclusive run mode (tray / Windows service) plus autostart and
auto-update on the Tasks page (pre-selected from what is installed on
upgrades, untouched by silent updates), 5 localized Start Menu entries.

Tray: theme-aware rounded menu with live status, icons and status-dot tray
icon; health polled off the UI thread; Settings submenu toggles autostart
and daily updates; browser opened de-elevated via explorer.

Fixes:
- tray Stop/Start was ignored in service mode (service_run restarted the
  children) - all start/stop now goes through runtime_ctl.ps1
- logon tray task and SYSTEM service task were killed after 72h (default
  ExecutionTimeLimit); autostart was registered for the elevating account
  and opened a browser on every logon
- uninstall left the NetXTray/NetXUpdate tasks behind
- silent auto-update killed the tray without restarting it
- repair_venv.ps1 was never staged into the release
- wildcard NETX_HOST (0.0.0.0) broke health checks
- ICO frames were PNG, which System.Drawing decodes as noise; icons now
  use the current brand mark

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

packaging/install_update_task.ps1

@@ -22,6 +22,11 @@ $checkPs1 = Join-Path $PSScriptRoot "check_update.ps1"
 
 if ($Remove) {
     Unregister-ScheduledTask -TaskName $taskName -TaskPath $taskPath -Confirm:$false -ErrorAction SilentlyContinue
+    # Tray also applies updates on launch when NETX_UPDATE_AUTO=true; turn that off too.
+    $envFile = Join-Path $data ".env"
+    if (Test-Path $envFile) {
+        Write-DotEnvValue -Path $envFile -Values @{ "NETX_UPDATE_AUTO" = "false" }
+    }
     Write-Host "==> Update task removed"
     exit 0
 }