we should autosend queued messages when back in connectivity

this is a 180 from previously, but in retrospect i'm pretty sure we should store queued messages, including across restarts, and resend them automatically as soon as the app has connectivity again, otherwise they get lost

The issue names no files or tests; start by locating the message-send and connectivity-handling entry points in the Swift iOS app. Define how queued messages persist across restarts and resend when connectivity returns, then verify they survive relaunch and are delivered after reconnection.

Written by the indexing model from the issue text.