Connect a remembered account on launch, as the desktop does

`frq.app/start!` has done this since it was written, and says why: a
remembered account has already said what it wants, and making it say so
again at every launch is a click that carries no information. The phone
restored the same session and then sat on the connect screen waiting to be
told a second time.

On a timer rather than awaited before the first frame, and for the
desktop's reason too — the connect screen with its status is what should be
on screen while it happens, so a failure lands somewhere visible instead of
in front of a window that has not been drawn.

Nothing changes for a guest: the whole thing is inside the `when-let` over
the saved session, so an install that has never signed in has nothing to
resume and still opens where it did.

Verified on a Pixel 6a: a cold launch with no taps reaches "Logged in as
nandi.uk" with the channels and their backlog.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>