Talk group switcher on main screen, auto-connect on launch

- Tapping the TG badge opens a group list; picking a group saves it and
  reconnects to the server with the new group
- Groups configured in settings (comma-separated), defaults 9,11,12,13
- Auto-connect at app launch to the default group from settings

app/src/main/res/values/strings.xml

@@ -9,6 +9,9 @@
     <string name="pref_callsign">Позывной</string>
     <string name="pref_auth_key">Пароль (AUTH_KEY)</string>
     <string name="pref_tg">Группа вещания (TG)</string>
+    <string name="pref_groups">Группы для переключения (через запятую)</string>
+    <string name="select_tg">Выбор группы</string>
+    <string name="toast_groups_empty">Добавьте группы в настройках</string>
     <string name="btn_save">Сохранить</string>
     <string name="app_version">SVXhomyak — v1.0.2</string>
     <string name="saved">Сохранено</string>
@@ -26,7 +29,7 @@
     <string name="meter_mic">MIC</string>
     <string name="meter_idle">---</string>
     <string name="meter_db">-%1$d dB</string>
-    <string name="tg_badge">TG%1$d</string>
+    <string name="tg_badge">TG%1$d ▾</string>
     <string name="talker_last_none">Последний: —</string>
     <string name="status_connecting">Подключение…</string>
     <string name="status_connecting_ssl">Проверка ключа…</string>