Fix race condition in BHapticsConnection.Initialize()

[Copilot]

The Initialize() method checked _isInitialized without synchronization, allowing concurrent threads to pass the guard simultaneously and attempt multiple initializations.

Changes

• Added _initializeLock to serialize initialization and shutdown
• Wrapped Initialize() method body in lock to prevent concurrent initialization attempts
• Protected _isInitialized write in Shutdown() with same lock

public static bool Initialize() {
    lock (_initializeLock) {
        if (_isInitialized) {
            ResoniteMod.Warn("Already initialized - skipping duplicate connection");
            return true;
        }
        
        // Connect to bHaptics Player
        bool connected = ModernBHaptics.bHapticsManager.Connect("Resonite", "Resonite", true, 10);
        // ...
        _isInitialized = true;
        return true;
    }
}

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