Curated catalog apps could be installed, stopped, and force-reinstalled,
but never removed — the only path off a device was manual docker + DB
surgery. Custom apps already had delete; this adds the equivalent for
curated apps.
POST /api/system/services/uninstall stops and removes the app's
container (optionally its image, same best-effort semantics as custom
app delete) and flips the record back to not-installed so the card
returns to the available catalog. Host bind-mount data is deliberately
left on disk, so a later reinstall picks the app back up where it left
off — unlike force-reinstall, which clears volumes.
Guards: custom apps are rejected (use delete), dependency services are
rejected, and uninstalling a not-installed app is a 409.
UI: installed curated cards get an Uninstall action in the card menu,
with a confirm modal that explains data is preserved and offers the
same remove-image checkbox as custom app delete.