Adds the Send files action to the device detail, routing the picked
selection through sendToContact.
Rather than a second picker path, sharePickedFiles now takes a
ShareDestination, so the macOS security-scoped access handling covers both
routes. A contact destination carries no access policy, matching the core's
rule that an offer share is never public.
Closes the loop: until now nothing in the UI could create a contact, so the
list stayed empty unless the peer initiated.
A completed receive names its sender and a completed delivery names its
receiver, so both sides get the suggestion. Declining is persisted, or every
later transfer with the same device would re-ask a question already
answered; pairing deliberately afterwards clears that.
The suggestion sheet ranks below the two other prompts, since nobody is
waiting on the answer.
MVVM model for the device list, its detail, and the two consent prompts.
Accepting an offer is the only path that returns a ticket, matching the
core: a declined offer hands over nothing.
Grant lifetime lives in preferences because the core holds it in memory
only, so it is pushed back on every start rather than silently reverting to
the default.
