bug: allowance added toasts replace each other when several offers arrive at once #1599

Refs: #1385 (comment)

What happened?

With notifications off, when several allowance offers are accepted automatically in one refresh, the "Allowance Added" toasts replace each other: each one dismisses the one before it, so only the last contact's toast stays readable.

Expected behavior

The user can read every "Allowance Added" announcement, for example as one combined toast or toasts that wait their turn.

Steps to Reproduce

1. Turn notifications off for Bitkit on the allowee's wallet.
2. Have two contacts each set an allowance for this wallet while it is closed.
3. Open Bitkit so both offers are accepted in the same refresh.

Logs / Screenshots / Recordings

announceAcceptedAllowanceOffers enqueues one fallback toast per offer, and ToastQueueManager.enqueue dismisses the current toast each time.

Bitkit Version

Allowances branch (not released yet).

Device / OS

Any Android device.

Reproducibility

Every time two or more offers are accepted in one refresh with notifications off.