Add a "Security" subsection to Settings → Backup & keys (open wallet only) that
wires the encryption controller methods to the UI:
- Unencrypted wallet: passphrase field + "Encrypt wallet".
- Encrypted + locked: "Unlock" (passphrase) ; Encrypted + unlocked: "Lock now".
- Encrypted: passphrase + "Remove encryption" (decrypt).
- Status line reflects the result; state shown from WalletState.isEncrypted()/
isLocked() (kept current by the controller's encryptionstatus refresh poll).
Secret hygiene: the passphrase inputs (lite_enc_pass / lite_dec_pass) are
sodium-zeroed immediately after each action and when the wallet closes while the
section was open.
Runtime-checked: app auto-opens a wallet and the new encryptionstatus worker poll
runs clean (no errors); tests pass; hygiene clean.
Follow-ups (not yet): a send-time unlock prompt and a startup lock-screen overlay
for an encrypted+locked wallet (today: unlock via Settings; balances remain
viewable while locked).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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