Replace the legacy Flatpak repo key with Bearwave App
<dev@bearwave.app> (5BAA384577671E45) in bearwave.flatpakref,
build-flatpak.sh, and deploy-flatpak.sh.
Unsigned summary updates left stale summary.sig files on the server,
causing BAD signature errors for clients. Sign exports and summaries
with the BearWave repo key and require .sig files before deploy.