TBB Backup 0.5.3: reopen from the desktop shortcut

If TBB Backup was already running in the system tray, opening its desktop shortcut tried to launch a second copy. The existing single-instance lock rejected it, and the launcher displayed a misleading message mentioning WebView2.

Version 0.5.3 sends a reopen request to the running app instead. The existing window is shown and restored, including when a backup is in progress. Repeated automatic Windows startup does not open an extra window. Allow a couple of seconds for the running app to handle the request.

The generic startup failure message no longer claims that WebView2 is missing for every startup error. Genuine failures still record details in startup-error.log.

## Upgrade
Close TBB Backup from its tray menu after any operation finishes, then install the update. Existing jobs and backup versions remain compatible. No WebView2 reinstall is required merely because of this second-launch error.

## Validation
50 backend tests ran: 49 passed and one archive-tool test was skipped because its executable was unavailable. New checks cover second-launch handoff, quiet automatic startup, reopening during a backup and requests arriving before the window is ready. JavaScript syntax and the installer NSIS length/CRC checks pass. Native Windows desktop/tray acceptance testing remains limited.

[Download TBB Backup](/apps/tbb-backup) · [Version 0.5.2 features](/patch-notes/tbb-backup-0-5-2)