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.

backend/tests/PnvPanel.Domain.Tests/Nodes/NodeTests.cs

@@ -120,6 +120,79 @@ public class NodeTests
         Assert.Equal(NodeStatus.Online, node.Status);
     }
 
+    [Fact]
+    public void RecordProbe_SingleFailure_DoesNotGoOffline_WhenThresholdNotReached()
+    {
+        var node = Node.Register("Node", new Uri("https://example.com"), Credentials, null);
+        node.UpdateStatus(NodeStatus.Online);
+
+        var changed = node.RecordProbe(reachable: false, failureThreshold: 2);
+
+        Assert.False(changed);
+        Assert.Equal(NodeStatus.Online, node.Status);
+        Assert.Equal(1, node.ConsecutiveProbeFailures);
+    }
+
+    [Fact]
+    public void RecordProbe_GoesOffline_OnlyAfterConsecutiveFailuresReachThreshold()
+    {
+        var node = Node.Register("Node", new Uri("https://example.com"), Credentials, null);
+        node.UpdateStatus(NodeStatus.Online);
+
+        Assert.False(node.RecordProbe(reachable: false, failureThreshold: 2));
+        Assert.Equal(NodeStatus.Online, node.Status);
+
+        var changed = node.RecordProbe(reachable: false, failureThreshold: 2);
+
+        Assert.True(changed);
+        Assert.Equal(NodeStatus.Offline, node.Status);
+        Assert.Equal(2, node.ConsecutiveProbeFailures);
+    }
+
+    [Fact]
+    public void RecordProbe_FlappingFailSuccess_NeverGoesOffline()
+    {
+        var node = Node.Register("Node", new Uri("https://example.com"), Credentials, null);
+        node.UpdateStatus(NodeStatus.Online);
+
+        // Чередование fail/success (ровно паттерн со скриншота) не должно ронять статус:
+        // порогу нужны ДВЕ подряд неудачи, а удачная проба обнуляет счётчик.
+        for (var i = 0; i < 5; i++)
+        {
+            Assert.False(node.RecordProbe(reachable: false, failureThreshold: 2));
+            Assert.False(node.RecordProbe(reachable: true, failureThreshold: 2));
+            Assert.Equal(NodeStatus.Online, node.Status);
+            Assert.Equal(0, node.ConsecutiveProbeFailures);
+        }
+    }
+
+    [Fact]
+    public void RecordProbe_SuccessAfterOffline_ReturnsOnlineImmediately_AndResetsCounter()
+    {
+        var node = Node.Register("Node", new Uri("https://example.com"), Credentials, null);
+        node.RecordProbe(reachable: false, failureThreshold: 2);
+        node.RecordProbe(reachable: false, failureThreshold: 2);
+        Assert.Equal(NodeStatus.Offline, node.Status);
+
+        var changed = node.RecordProbe(reachable: true, failureThreshold: 2);
+
+        Assert.True(changed);
+        Assert.Equal(NodeStatus.Online, node.Status);
+        Assert.Equal(0, node.ConsecutiveProbeFailures);
+    }
+
+    [Fact]
+    public void RecordProbe_SuccessWhenAlreadyOnline_ReportsNoChange()
+    {
+        var node = Node.Register("Node", new Uri("https://example.com"), Credentials, null);
+        node.UpdateStatus(NodeStatus.Online);
+
+        var changed = node.RecordProbe(reachable: true, failureThreshold: 2);
+
+        Assert.False(changed);
+        Assert.Equal(NodeStatus.Online, node.Status);
+    }
+
     [Fact]
     public void MarkSynced_SetsLastSyncAt()
     {