[Cashtab] Deprecate api-only app mgmt methods

Summary: Cashtab no longer has API-only functionality. Deprecate legacy tx notifications for disconnected websocket runtime.

Test Plan:
npm test
grep -r usePrevious src/ and no output

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15663