Some fixes

[dewabisma]

Note

Low Risk
Small UI/validation tweaks on account screens and removal of a non-functional mining button; no auth, payments, or persistence logic changes.

Overview
Tightens account name flows and hides unfinished mining redeem UI.

Create account drops inline _error on NameField and no longer disables the primary action because of that state. The create button stays disabled only when the trimmed name is empty or a create is in progress.

Edit account now disables Done when the trimmed name is empty, matching create behavior and avoiding a no-op save tap (empty names still show a toaster in _save if reached).

Mining rewards removes the bottom Redeem bar (it had onTap: null) and comments it with a TODO until redeem is implemented; related button/scaffold imports are removed.

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