v0.3.0 — phone-switch day, made easy.

* Bulk backup: every paired relationship in one encrypted file, one
  8-word PAKE. Settings → Back up all relationships.
* Single-relationship backup (per-contact menu) still works the same.
* Import auto-routes on payload-type — paste any Signet backup and
  the app picks the right commit flow.

Existing pairings migrate untouched on update. Issues:
https://github.com/digital-grease/signet/issues
