F1.31 About shows where settings and data are kept, each with Copy #306

Spec: to write first (docs/features/F1.31-…), from the scope row. A maintainer request (2026-10-19).

Help › About (F1.29 behavior 10) gets a Files part listing each place the app keeps something, with its full path and a Copy button that puts it on the clipboard. This is for troubleshooting, backups and reading files by hand.

• Desktop: the folders from F4.15 behavior 13, as this system has them:
  • Settings: profiles, sources, appearance, layouts. On Linux ~/.config/aprsnet/aprsmap.
  • Data: message history, packet captures. On Linux ~/.local/share/aprsnet/aprsmap.
  • Cache: map tiles, the downloaded device list (F4.16). On Linux ~/.cache/aprsnet/aprsmap.
  • Defaults for every user, read only. On Linux /etc/xdg/aprsnet/aprsmap.
  • A folder given with --settings-folder or Engine:SettingsFolder/DataFolder is shown as it is, saying it was set.
• Gateway: the server's folders (/data and so on) only for a signed-in operator (F2.9); viewers never see the server's paths. Every viewer is told that this browser keeps its own layout and appearance in its own storage.
• Copy: each path has its own Copy button, with an accessible name such as "Copy the settings folder". Where there's no clipboard (a browser off HTTPS or localhost), the button is hidden and the path stays selectable, as with the passcode calculator.
• Engine: reports the folders itself (an IEngineService member, operator-only on a gateway), so the desktop and the web show the same.

Later, not in this issue: an Open folder button on the desktop.