Normalize base address in Node class to ensure consistent URI formatting

- Implemented `NormalizeBaseAddress` method to add a trailing slash to the `BaseAddress` when necessary, preventing issues with relative path merging in 3x-ui deployments.
- Updated `Register` and `UpdateAddress` methods to utilize the normalization logic, ensuring that both methods handle base address input consistently.
- Added unit tests to verify the normalization behavior for various input scenarios, enhancing the reliability of node address management.
- Updated domain model documentation to reflect the new normalization behavior for `BaseAddress`.

backend/src/PnvPanel.Domain/Nodes/Node.cs

@@ -34,7 +34,7 @@ public sealed class Node : Entity
         {
             Id = Guid.NewGuid(),
             Name = name,
-            BaseAddress = baseAddress,
+            BaseAddress = NormalizeBaseAddress(baseAddress),
             Credentials = credentials,
             Location = location,
             Status = NodeStatus.Unknown,
@@ -54,9 +54,18 @@ public sealed class Node : Entity
         if (!baseAddress.IsAbsoluteUri)
             throw new DomainException("Адрес ноды должен быть абсолютным URI.");
 
-        BaseAddress = baseAddress;
+        BaseAddress = NormalizeBaseAddress(baseAddress);
     }
 
+    /// <summary>3x-ui часто разворачивается за нестандартным base path (`webBasePath`, напр.
+    /// `/benis`) — без завершающего слэша относительное объединение пути (RFC 3986 merge) отбрасывает
+    /// последний сегмент базы вместо добавления к нему, роняя `/benis` из итогового URL. Нормализуем
+    /// один раз при сохранении, чтобы админ мог вводить адрес и с завершающим слэшем, и без него.</summary>
+    private static Uri NormalizeBaseAddress(Uri baseAddress) =>
+        baseAddress.AbsolutePath.EndsWith('/')
+            ? baseAddress
+            : new UriBuilder(baseAddress) { Path = baseAddress.AbsolutePath + "/" }.Uri;
+
     public void UpdateCredentials(NodeCredentials credentials) => Credentials = credentials;
 
     public void Enable() => IsEnabled = true;