Created / Updated fields for clients (#3384)

* feat(backend): add created_at/updated_at to clients and maintain on create/update
backfill existing clients and set updated_at on mutations

* feat(frontend): carry created_at/updated_at in client models and round-trip via JSON

* feat(frontend): display Created and Updated columns in client table with proper date formatting

* i18n: add pages.inbounds.createdAt/updatedAt across all locales

* Update inbound.go

Remove duplicate code

web/translation/translate.ru_RU.toml

@@ -165,6 +165,8 @@
 "details" = "Подробнее"
 "transportConfig" = "Транспорт"
 "expireDate" = "Дата окончания"
+"createdAt" = "Создано"
+"updatedAt" = "Обновлено"
 "resetTraffic" = "Сброс трафика"
 "addInbound" = "Создать инбаунд"
 "generalActions" = "Общие действия"