Improve i18n for authenticator setup instructions

Added new resource strings (prefix, link, suffix) for authenticator app setup instructions in German, English, and French resource files. Updated EnvelopeLocked.cshtml to assemble the instruction dynamically using these localized parts, ensuring correct grammar and flexibility across supported languages.

EnvelopeGenerator.Web/Views/Envelope/EnvelopeLocked.cshtml

@@ -38,12 +38,12 @@
     {
     <section class="text-center">
         <p class="m-0 p-0">
-            Klicken Sie auf den
+                @_localizer["AuthenticatorSetup_Prefix"]
             <a class="icon-link m-0 p-0" href="/tfa/@envelopeKey" style="text-decoration: none;" target="_blank">
-                Link
+                    @_localizer["AuthenticatorSetup_Link"]
                 <i class="bi bi-box-arrow-up-right"></i>
             </a>
-             um Ihre Authenticator-App einzurichten.
+                @_localizer["AuthenticatorSetup_Suffix"]
         </p>
     </section>
     }