feat(auth): say when an account signs in with its password

A code by mail no longer signs into an account with a password and an
authenticator; email sign-in now says so rather than failing unnamed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_app/lib/l10n/halkyon_app_localizations_en.dart

@@ -262,6 +262,10 @@ class HalkyonAppLocalizationsEn extends HalkyonAppLocalizations {
   String get emailSignInMailFailed =>
       'The instance couldn\'t send the mail. Try again later.';
 
+  @override
+  String get emailSignInUsePassword =>
+      'This account signs in with its password and an authenticator app.';
+
   @override
   String get emailSignInFailed => 'Couldn\'t reach the instance. Try again.';