Pushes configured phone folders (DCIM, WhatsApp media, call recordings, and
so on) to one or more home SSH hosts using rsync over SSH. One-way push
only, on an unmetered network by default, periodic or on demand.

rsync and the SSH transport are built from source and shipped inside the APK.
The app needs all-files access to read arbitrary backup folders such as OEM
call-recording directories.

Features:

* Multiple named remotes; each folder picks its destination host.
* Incremental transfers; large videos resume from a private partial directory.
* Per-folder deletion policy: additive backup or mirror.
* Runs on an unmetered network, periodically or on demand.
* Ed25519 client-key auth with strict, pinned host-key verification.
