Fix Toast Notifications and Frontend Feedback Consistency

### Description

Standardize toast responses per action to reflect accurate backend status. Tasks include:

* Ensure **successful toast messages** match the actual operation (e.g., "Top-up successful" should not appear for transfers or withdrawals).
* Make sure **balance checks**, **see all transactions**, **device registration**, and **initialization** return backend responses.
* Eliminate hardcoded frontend messages in favor of **dynamic responses** from the backend.