feat: filter inbounds and clients by node (#4997)

Multi-node panels had no way to narrow the inbounds or clients lists to
a single node. Add a node filter to both pages:

- Inbounds: a toolbar select (All / Local / each node) that filters the
  list client-side; shown only when the panel has nodes or node-attached
  inbounds.
- Clients: a Nodes multi-select in the filter drawer. Node selections
  are mapped onto inbound IDs client-side and fed through the existing
  inbound CSV paging parameter, so the paging backend is untouched; an
  impossible id (-1) is sent when no inbound matches so the filter
  yields an honest empty result. InboundOption now carries nodeId to
  make the mapping possible.

The local panel is selectable via a 0 sentinel (inbounds without a
nodeId). New i18n keys in all 13 locales.

internal/web/translation/ru-RU.json

@@ -673,6 +673,10 @@
       "searchPlaceholder": "Поиск email, комментария, sub ID, UUID, пароля, auth…",
       "filterTitle": "Фильтр клиентов",
       "clearAllFilters": "Очистить все",
+      "filters": {
+        "nodes": "Узлы",
+        "localPanel": "Локально (эта панель)"
+      },
       "showingCount": "Показано {shown} из {total}",
       "sortOldest": "Сначала старые",
       "sortNewest": "Сначала новые",