🧪 Add NetworkModelCloneUtilityTests

[google-labs-jules]

🎯 What: Added tests to address the missing test coverage for NetworkModelCloneUtility in src/MedWNetworkSim.App/Services/NetworkModelCloneUtility.cs. Also fixed a SkiaSharp dependency issue in the test project to ensure all tests run cleanly.

📊 Coverage:

• Clone_ReturnsNewInstance: Verifies the cloned network is a new instance.
• Clone_CopiesSerializedProperties: Ensures serialized properties and nested lists (Nodes, Edges) are correctly copied.
• Clone_IgnoresJsonIgnoreProperties: Ensures properties marked with [JsonIgnore] are deliberately not copied and retain default values.

✨ Result: Enhanced test coverage specifically tailored to ensure accurate JSON cloning behavior for the simulation network model without side-effects.

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PR created automatically by Jules for task 2270455722502062832 started by @wnj00524

[google-labs-jules]

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