feat(observability): phases 4-7 - complete frontend UI (big bang)

Add all frontend pages for observability & proxy management:
- Proxy Viewer: /proxies with grouped view, filtering, health indicators
- Proxy Creation: form with live validation, diagnostic hints, edit/delete
- Stale Containers: /containers/stale with dashboard widget, cleanup actions
- Event Log: /events with filters, pagination, real-time SSE streaming
- Navigation: proxies and events links in sidebar
- i18n: full EN/RU translations for all new features
- Settings: stale threshold configuration

web/src/lib/api.ts

@@ -13,6 +13,7 @@ import type {
 	Registry,
 	RegistryImage,
 	Settings,
+	StaleContainer,
 	Stage,
 	StageEnv,
 	StandaloneProxy,
@@ -405,4 +406,18 @@ export function listAllProxies(): Promise<ProxyView[]> {
 	return get<ProxyView[]>('/api/proxies/all');
 }
 
+// ── Stale Containers ────────────────────────────────────────────────
+
+export function fetchStaleContainers(): Promise<StaleContainer[]> {
+	return get<StaleContainer[]>('/api/containers/stale');
+}
+
+export function cleanupStaleContainer(id: string): Promise<{ deleted: string }> {
+	return post<{ deleted: string }>(`/api/containers/stale/${id}/cleanup`);
+}
+
+export function bulkCleanupStaleContainers(): Promise<{ deleted: number }> {
+	return post<{ deleted: number }>('/api/containers/stale/cleanup');
+}
+
 export { ApiError };