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

@@ -35,6 +35,29 @@ public class NodeTests
         );
     }
 
+    [Theory]
+    [InlineData("https://host.example.com/benis", "https://host.example.com/benis/")]
+    [InlineData("https://host.example.com/benis/", "https://host.example.com/benis/")]
+    [InlineData("https://host.example.com", "https://host.example.com/")]
+    public void Register_NormalizesBaseAddressToTrailingSlash(string input, string expected)
+    {
+        var node = Node.Register("Node", new Uri(input), Credentials, null);
+
+        Assert.Equal(expected, node.BaseAddress.ToString());
+    }
+
+    [Theory]
+    [InlineData("https://host.example.com/benis", "https://host.example.com/benis/")]
+    [InlineData("https://host.example.com/benis/", "https://host.example.com/benis/")]
+    public void UpdateAddress_NormalizesBaseAddressToTrailingSlash(string input, string expected)
+    {
+        var node = Node.Register("Node", new Uri("https://old.example.com"), Credentials, null);
+
+        node.UpdateAddress(new Uri(input));
+
+        Assert.Equal(expected, node.BaseAddress.ToString());
+    }
+
     [Fact]
     public void UpdateDetails_ChangesNameAndLocation()
     {