feat: multi-select tariff filter, select-all subscriptions, auto-expand

1. Tariff filter: replace single-select dropdown with MultiSelectDropdown
   component — checkboxes for each tariff, "Select all" / "Deselect all"
   controls, shows selected names or count in button label
2. Client-side subscription filtering: when tariffs selected in filter,
   only show matching subscriptions in expanded sub-rows
3. "Select all subscriptions" button in FloatingActionBar — toggles all
   visible subscription checkboxes and auto-expands relevant rows
4. Auto-expand: all user rows with multiple subscriptions are expanded
   by default when data loads (no need to click chevron)
5. i18n: new keys for tariff multi-select and subscription select-all

src/locales/ru.json

@@ -3826,7 +3826,10 @@
         "promoGroup": "Промогруппа",
         "allStatuses": "Все статусы",
         "allTariffs": "Все тарифы",
-        "allGroups": "Все группы"
+        "allGroups": "Все группы",
+        "tariffsSelected": "{{count}} тарифов",
+        "selectAll": "Выбрать все",
+        "deselectAll": "Снять все"
       },
       "statuses": {
         "active": "Активна",
@@ -3853,7 +3856,9 @@
       "userTarget": "Цель: пользователи",
       "daysUnit": "дн.",
       "trafficOf": "из",
-      "trafficGbUnit": "ГБ"
+      "trafficGbUnit": "ГБ",
+      "selectAllSubs": "Выбрать все подписки",
+      "deselectAllSubs": "Снять все подписки"
     },
     "theme": {
       "accentColor": "Акцентный цвет",