feat: confirm before leaving a game, and fix untranslated strings

Exit confirmation
- A dialog in the app's own style now guards every in-game screen. The safe
  action is the prominent one, so a stray tap keeps you in the game.
- Eleven screens covered, against both the system back gesture and the close
  buttons. The message adapts: a single-device game is lost, a host ends it
  for everyone, a client can rejoin.
- The two screens the host also opens from the manager take a flag so that
  back there just closes them instead of offering to quit.

Translations
- 21 keys were still holding the English text in Arabic, Basque, Hindi,
  Japanese, Korean, Dutch, Polish, Russian, Turkish and both Chinese
  variants: 231 strings, covering the whole multi-device flow, permissions
  and the mode picker. Nothing failed, the app just showed English.
- The permissions dialog was hardcoded in Spanish; it is localized now.
- Portuguese used Spanish gerunds where pt-PT takes "a + infinitive".

Checked what looked untranslated but is not: Animals and Notes are correct
Catalan, Configuration and Vibration correct French, Version correct German.
Those are whitelisted in the new test rather than silently rewritten.

l10n_cobertura_test guards all of it: no missing or orphan keys, no empty
values, no English left outside the whitelist, and placeholders preserved.

lib/pantallas/pantalla_lobby_host.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import '../tema/dialogo_confirmacion.dart';
 import 'package:provider/provider.dart';
 import 'package:qr_flutter/qr_flutter.dart';
 import 'package:farolero/l10n/generated/app_localizations.dart';
@@ -42,6 +43,12 @@ class _PantallaLobbyHostState extends State<PantallaLobbyHost> {
         leading: IconButton(
           icon: IconoFarolero(Icons.close),
           onPressed: () async {
+            if (!await confirmarSalirDePartida(
+              context,
+              ContextoSalida.host,
+            )) {
+              return;
+            }
             await nearby.desconectar();
             if (context.mounted) Navigator.pop(context);
           },