fix: add listen: false to showToolbar() and hideToolbar()

[nateshmbhat]

Description

Fixes #278

Adds listen: false parameter to Provider.of<DevicePreviewStore>() calls in showToolbar() and hideToolbar() methods to prevent assertion errors when called from event handlers.

Changes

Only two lines changed:

• Line 245: Added , listen: false to showToolbar() method
• Line 257: Added , listen: false to hideToolbar() method

Why This Fix is Needed

Without listen: false, calling these methods from event handlers (button onPressed, switch onChanged, etc.) throws:

Tried to listen to a value exposed with provider, from outside of the widget tree.
Failed assertion: 'context.owner!.debugBuilding || listen == false || debugIsInInheritedProviderUpdate'

Consistency

This makes both methods consistent with other static methods in the same file like selectDevice() and availableDeviceIdentifiers() which already use listen: false.

Testing

Verified with a switch widget calling these methods - no more errors:

Switch(
  value: isVisible,
  onChanged: (value) {
    value ? DevicePreview.showToolbar(context) : DevicePreview.hideToolbar(context);
  },
)