Add optional password-encrypted persistence for full accounts

Per-account "Save on this device" encrypts a seed account into a
localStorage vault (scrypt KDF + XChaCha20-Poly1305 via @noble), so it
survives a browser close. On reopen, a vault prompt unlocks all saved
wallets with the password (or "Use another wallet" to skip). Default
stays session-only; the password is held only in memory for the session
and re-encrypts on save/forget. Wrong password fails closed (AEAD).
Adds @noble/ciphers dependency. New strings translated across all 19
locales.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/i18n.js b/src/i18n.js
index f75e014..9a48796 100644
--- a/src/i18n.js
+++ b/src/i18n.js
@@ -49,6 +49,23 @@ const STR = {
     labelOptional: 'Label (optional)',
     walletLabelN: 'Wallet {n}',
     watchLabelN: 'Watch {n}',
+    saveDevice: 'Save on this device',
+    forgetDevice: 'Saved · forget',
+    savedTag: 'saved',
+    setPassword: 'Set a password',
+    setPasswordDesc: 'Encrypts this wallet on this device. You will need it to unlock saved wallets later.',
+    enterPassword: 'Enter your password',
+    enterPasswordDesc: 'Unlock your saved wallets to continue.',
+    password: 'Password',
+    confirmPassword: 'Confirm password',
+    pwTooShort: 'Use at least 8 characters.',
+    pwMismatch: 'Passwords do not match.',
+    pwWrong: 'Wrong password.',
+    unlockSaved: 'Unlock saved wallets',
+    unlockSavedDesc: 'Enter your password to open the wallets saved on this device.',
+    unlock: 'Unlock',
+    useAnotherWallet: 'Use another wallet',
+    save: 'Save',
     publicKey: 'Public key',
     publicKeyDesc: 'Share this to watch this wallet read-only on another device or app. It reveals your addresses, not your keys.',
     copyKey: 'Copy key',