Add Barcode scanner button

This adds a button to launch the QRCA barcode scanner application in Wifi scanner mode to easily connect to Wifi networks via QR code.

If QRCA is not available, it offers to install it instead.

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“out of process” alternative to !178 (closed)

Since QRCA hasn’t been officially released before 25.04 which already includes the Wifi scanner, I don’t think we need to check for that.

@davidedmundson @ngraham @vkrause