#11 explain SCRAM proof mismatches and make the password visible

- Translate Prosody's "doesn't match the one we calculated" SCRAM
  failure into an actionable Russian message pointing at the typed
  password, since the client math itself is verified against the
  RFC 5802 test vector.
- Set explicit username/password text content types on the login
  screen, disable smart text features, and add a password visibility
  toggle so users can verify what they submit.
- Cover the mapping with a unit test and verify.sh invariants.

Scripts/verify.sh

@@ -313,6 +313,14 @@ grep -q 'Сервер отклонил имя пользователя или п
   echo "SASL failures must produce an actionable Russian message"
   exit 1
 }
+grep -q "doesn't match the one we calculated" Sources/Shared/XMPP/SaslFailureMessage.swift || {
+  echo "Prosody SCRAM proof mismatches must be explained in Russian"
+  exit 1
+}
+grep -q 'passwordVisible' Sources/Shared/UI/LoginView.swift || {
+  echo "The login screen must let the user verify the typed password"
+  exit 1
+}
 grep -q 'func deleteGroupChat' Sources/Shared/Models/AppModel.swift || {
   echo "Group chats must support local deletion"
   exit 1