fix(clients): include Telegram ID in client list search (#5888)

* fix(clients): include Telegram ID in client list search

clientMatchesSearch only checked Email/SubID/Comment/UUID/Password/Auth,
so searching the client list for a Telegram user ID never matched even
though the field is stored on every client.

This is a real regression, not a field that was simply never included:
before the paged search endpoint (#4500), the frontend searched with
ObjectUtil.deepSearch() over the full client object, which recursed into
every field including tgId. Replacing that with a fixed backend field
list silently dropped it (along with a few other fields, but tgId is the
one that's actually needed here since it's the panel's own way of
looking a client up when it only knows their Telegram ID).

TgID is int64 (0 = unset), so it can't sit in the existing []string
candidates array — matched separately via strconv, and skipped when 0 to
avoid a needle of "0" spuriously matching every client without a
Telegram ID.

Fixes #5880

* fix(clients): drop explanatory comment, mention Telegram ID in search hint

Addresses review feedback on #5888:
- Removed the // comment block above the TgID check in
  clientMatchesSearch per repo convention (code should read on its own).
- Updated searchPlaceholder in all 13 locale files to mention Telegram ID,
  since the search box now actually matches on it.

* test(clients): remove TgID search test per maintainer request

internal/web/translation/ru-RU.json

@@ -775,7 +775,7 @@
       "renew": "Автопродление",
       "renewDesc": "Автоматическое продление после окончания. (0 = отключено) (единица: день)",
       "renewDays": "Автопродление (дней)",
-      "searchPlaceholder": "Поиск email, комментария, sub ID, UUID, пароля, auth…",
+      "searchPlaceholder": "Поиск email, комментария, sub ID, UUID, пароля, auth, Telegram ID…",
       "filterTitle": "Фильтр клиентов",
       "clearAllFilters": "Очистить все",
       "filters": {