feat: Add unit tests and fakes for Crestron environment and data store

- Introduced `FakeCrestronEnvironment` and `FakeEthernetHelper` for testing purposes.
- Implemented `InMemoryCrestronDataStore` to facilitate unit tests for data storage.
- Created `DebugServiceTests` to validate the behavior of debug-related services.
- Added project files for unit tests targeting .NET 9.0 with necessary dependencies.
- Developed production adapters (`CrestronConsoleAdapter`, `CrestronDataStoreAdapter`, `CrestronEnvironmentAdapter`, `CrestronEthernetAdapter`) to interface with the Crestron SDK.
- Updated `Debug` class to utilize injected service abstractions instead of direct SDK calls.
- Enhanced `ControlSystem` initialization to register service adapters before usage.

src/PepperDash.Core.Abstractions/DebugServiceRegistration.cs

@@ -0,0 +1,36 @@
+namespace PepperDash.Core.Abstractions;
+
+/// <summary>
+/// Allows pre-registration of Crestron service implementations before the <c>Debug</c>
+/// static class initialises. Call <see cref="Register"/> from the composition root
+/// (e.g. ControlSystem constructor) <em>before</em> any code touches <c>Debug.*</c>.
+/// Test projects should call it with no-op / in-memory implementations so that the
+/// <c>Debug</c> static constructor never tries to reach the real Crestron SDK.
+/// </summary>
+public static class DebugServiceRegistration
+{
+    /// <summary>Gets the registered environment abstraction, or <c>null</c> if not registered.</summary>
+    public static ICrestronEnvironment? Environment { get; private set; }
+
+    /// <summary>Gets the registered console abstraction, or <c>null</c> if not registered.</summary>
+    public static ICrestronConsole? Console { get; private set; }
+
+    /// <summary>Gets the registered data-store abstraction, or <c>null</c> if not registered.</summary>
+    public static ICrestronDataStore? DataStore { get; private set; }
+
+    /// <summary>
+    /// Registers the service implementations that <c>Debug</c> will use when its
+    /// static constructor runs. Any parameter may be <c>null</c> to leave the
+    /// corresponding service unregistered (the <c>Debug</c> class will skip that
+    /// capability gracefully).
+    /// </summary>
+    public static void Register(
+        ICrestronEnvironment? environment,
+        ICrestronConsole? console,
+        ICrestronDataStore? dataStore)
+    {
+        Environment = environment;
+        Console = console;
+        DataStore = dataStore;
+    }
+}