Enhance user management and node health check features

- Updated `ListUsersQueryHandler` to include plan names and config quotas in `UserSummaryDto`, enriching user data retrieval.
- Implemented `WithPlanNamesAsync` method to fetch plan names based on user plan IDs, improving user experience in the admin interface.
- Enhanced `Node` class with a `ConsecutiveProbeFailures` property for better status management during health checks.
- Modified `NodeHealthCheckService` to utilize the new `RecordProbe` method, implementing a hysteresis mechanism for node status changes.
- Updated frontend components to display user config quotas and plan names, improving clarity in user management.
- Enhanced tests for user listing and node status handling to ensure robust functionality and coverage.
- Updated documentation to reflect changes in user and node management features.

docs/api-design.md

@@ -382,6 +382,13 @@ approve/reject над `ActivationRequest`.
 отличие от `VpnConfigDto`): `{ id, userId, userName, label, clientEmail, protocol, location, nodeName,
 usedUpBytes, usedDownBytes, expiresAt, status, createdAt }`. `search` матчится по `clientEmail`/`label`.
 
+`UserSummaryDto`: `{ id, userName, role, isActivated, isBlocked, activatedAt, billingEnabled,
+billingPaidUntil, configQuota, planId, billingPendingReview, planName }`. `configQuota` — фактическая
+квота конфигов (`-1` = без лимита), `planName` — имя каталожного тарифа по `planId` (`null`, если
+квота задана вручную); и `planName`, и `billingPendingReview` домешивает `ListUsersQueryHandler` —
+`IIdentityService` не знает ни про `Plans`, ни про `PaymentRequests`. Менять квоту админ может через
+`PATCH /api/admin/users/{id}/plan` (см. Admin — Roles & Plans), доплата при этом не создаётся.
+
 **Блокировка/разблокировка — два отдельных эндпоинта без тела**, не один переключатель `isBlocked`.
 `StatsDto`: `{ totalUsers, activatedUsers, pendingActivationRequests, totalNodes, onlineNodes,
 totalConfigs, activeConfigs, totalUsedUpBytes, totalUsedDownBytes }` — считается на лету при запросе,