Some fixes

[dewabisma]

Note

Low Risk
Small Flutter UI/validation tweaks with no auth, payments, or backend changes.

Overview
Tightens account naming flows so primary actions stay disabled when the name is only whitespace, and simplifies create-account UI by dropping inline field error state (failures still use toasters on submit).

On create account, the create button uses trim().isEmpty for disable logic and no longer blocks on a removed _error flag; NameField no longer receives an error prop. On edit account, Done is disabled the same way until a non-empty trimmed name is entered.

On mining rewards, the placeholder redeem footer (null onTap) is commented out with a TODO until redeem is implemented, and unused button/scaffold imports are removed.

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