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/l10n/app_pt.arb

@@ -6,7 +6,7 @@
   "matchRewards": "Recompensas da partida",
   "newMedals": "Novas medalhas",
   "noNewMedalsKeepFire": "Sem medalhas novas desta vez. Continua a acumular fogo.",
-  "calculatingRewards": "Calculando recompensas...",
+  "calculatingRewards": "A calcular recompensas...",
   "fireLabel": "Fogo",
   "playersRange": "3-20 jogadores  •  Sem internet",
   "createGame": "Criar partida",
@@ -85,7 +85,7 @@
   },
   "holdToSeeWord": "Mantenha pressionado para ver sua palavra",
   "makeSureNoOneLooks": "Certifique-se de que ninguém mais está olhando",
-  "showingWord": "👁️ Mostrando...",
+  "showingWord": "👁️ A mostrar...",
   "holdToSee": "👆 Mantenha pressionado para ver",
   "seenMyWord": "Já vi minha palavra",
   "debateRound": "Debate - Rodada {round}",
@@ -133,7 +133,7 @@
   "tapToReveal": "Toque para revelar o resultado",
   "revealResult": "Revelar resultado",
   "result": "Resultado",
-  "revealing": "Revelando...",
+  "revealing": "A revelar...",
   "wasImpostor": "Era IMPOSTOR! 🎉",
   "wasInnocent": "Era INOCENTE 😱",
   "votesThisRound": "Votos desta rodada",
@@ -368,5 +368,19 @@
   "reconnecting": "A religar...",
   "reconnectingHint": "Perdeu-se a ligação ao anfitrião. O teu lugar no jogo mantém-se.",
   "leaveGame": "Sair do jogo",
-  "playerRejoined": "{name} voltou ao jogo"
+  "playerRejoined": "{name} voltou ao jogo",
+  "leaveGameTitle": "Sair do jogo?",
+  "leaveGameSingleDevice": "O jogo em curso perde-se e não poderá ser recuperado.",
+  "leaveGameHost": "És o anfitrião: se saíres, o jogo termina para todos os jogadores.",
+  "leaveGameClient": "Vais sair do jogo. Podes voltar enquanto o anfitrião o mantiver aberto.",
+  "stayInGame": "Continuar a jogar",
+  "permissionsNeededTitle": "Permissões necessárias",
+  "permissionsNeededBody": "Para o modo multijogador precisamos de:",
+  "openAppSettingsQuestion": "Abrir as definições da aplicação?",
+  "openSettings": "Abrir definições",
+  "permissionLocation": "Localização",
+  "permissionBluetoothAdvertise": "Bluetooth (anunciar)",
+  "permissionBluetoothConnect": "Bluetooth (ligar)",
+  "permissionBluetoothScan": "Bluetooth (procurar)",
+  "permissionNearbyWifi": "Wi-Fi por perto"
 }