fix(lite): require a confirmed 8+ character passphrase to encrypt

The Lite "Encrypt wallet" field and the Create/Restore passphrase had no
confirmation and no minimum length; only an empty passphrase was
refused. Encrypting locks the wallet at once, and a locked wallet cannot
reveal its seed, so a typo there could cost a user without a seed backup
their funds. The full-node encrypt dialog already requires 8 characters
and a confirmation.

This applies to new passphrases only. Opening and unlocking are
unchanged: an existing wallet with a shorter passphrase still opens and
unlocks.

- A pure liteEncryptPassphraseValid(pass, confirm): at least 8 bytes and
  equal to the confirmation. It takes string_views, so the page's secret
  buffers are never copied.
- liteLifecyclePassphraseAcceptable(op, pass, confirm) gates the Settings
  create/open/restore request. Open is never checked, because its
  passphrase field also unlocks an existing wallet. Create and Restore
  are checked only when a passphrase was entered; an empty one still
  creates an unencrypted wallet.
- Encrypt gets a Confirm field. The button stays disabled until the
  passphrase is valid, and a hint says why (too short, with the count,
  or not matching).
- Create/Restore show a Confirm row once a passphrase is typed, with the
  same hint. Validate stays disabled while the passphrase is invalid, so
  a click never wipes a typed seed over a passphrase typo. The request
  builder re-checks the rule.
- The confirmation buffers are wiped with their passphrase: after a run
  or an encrypt, and when the Confirm row is hidden.
- Once the wallet is closed, the Settings page wipes the Encrypt,
  Confirm and Decrypt passphrase buffers whole every time, also when no
  secret was revealed; before, closing the wallet wiped them only while
  clearing a revealed backup or secret. They are zeroed in full because
  an emptied field can still hold the old tail past its first NUL.
- New copy under Encrypt: "Anyone with the wallet file can try
  passphrases offline. Back up your seed phrase first and use a long
  passphrase."
- i18n: three new keys (lite_confirm_label, tt_lite_confirm_pass,
  lite_encrypt_offline_warning) in i18n.cpp and the 8 language files,
  added additively. The hints reuse the wizard's wiz_pass_too_short and
  wiz_pass_mismatch. No new CJK glyphs, so the subset font is unchanged.

Tests: the validator rejects empty, short (7) and mismatched or
unconfirmed passphrases, and accepts 8 or more with a match. The request
gate always accepts Open, even "abc" with no confirmation, accepts
Create/Restore without a passphrase, and applies the rule to them
otherwise. An encrypted, locked wallet still opens and unlocks through
the controller with the 3-character passphrase "abc".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/util/i18n.cpp

@@ -826,6 +826,7 @@ void I18n::loadBuiltinEnglish()
         strings_["tt_lite_import_key"] = "Paste a private spending or viewing key to import; its history appears after the next sync";
         strings_["tt_lite_import_key_btn"] = "Import the entered private key into this wallet; funds and history appear after the next sync";
         strings_["tt_lite_encrypt_pass"] = "Passphrase to encrypt the wallet with. If lost, the wallet cannot be unlocked or recovered";
+        strings_["tt_lite_confirm_pass"] = "Type the new passphrase again; it must match and be at least 8 characters long";
         strings_["tt_lite_encrypt"] = "Encrypt the wallet with the passphrase above; it locks immediately and requires the passphrase to unlock";
         strings_["tt_lite_unlock_pass"] = "Enter your passphrase to unlock the encrypted wallet";
         strings_["tt_lite_unlock"] = "Unlock the encrypted wallet using the passphrase above";
@@ -943,6 +944,7 @@ void I18n::loadBuiltinEnglish()
         strings_["lite_account_label"] = "Account";
         strings_["lite_overwrite"] = "Overwrite";
         strings_["lite_passphrase_label"] = "Passphrase";
+        strings_["lite_confirm_label"] = "Confirm";
         strings_["lite_validate"] = "Validate";
         strings_["lite_working"] = "Working…";
         strings_["lite_enter_wallet_path"] = "Enter a wallet path";
@@ -967,6 +969,7 @@ void I18n::loadBuiltinEnglish()
         strings_["lite_key_import_failed"] = "Couldn't import the key \xE2\x80\x94 check it, unlock the wallet (if encrypted) and try again.";
         strings_["lite_security"] = "Security";
         strings_["lite_encrypt_wallet"] = "Encrypt wallet";
+        strings_["lite_encrypt_offline_warning"] = "Anyone with the wallet file can try passphrases offline. Back up your seed phrase first and use a long passphrase.";
         strings_["lite_wallet_encrypted"] = "Wallet encrypted";
         strings_["lite_unlock"] = "Unlock";
         strings_["lite_wallet_unlocked"] = "Wallet unlocked";