fix: multi-tariff filter now works server-side + trial-only checkbox

- Send comma-separated tariff_ids to backend (was only single ID)
  — server now filters with IN() operator, pagination correct
- Remove client-side tariff filtering (server handles it)
- Add "Только триал" checkbox filter: amber checkbox, filters users
  with trial subscriptions client-side
- Remove "trial" from status dropdown (was not working via
  subscription_status server filter)
- i18n: trialOnly key (ru + en)

src/locales/en.json

@@ -2086,6 +2086,7 @@
         "allStatuses": "All statuses",
         "allTariffs": "All tariffs",
         "allGroups": "All groups",
+        "trialOnly": "Trial only",
         "tariffsSelected": "{{count}} tariffs",
         "selectAll": "Select all",
         "deselectAll": "Deselect all"