Add QR code scanner for frontend

[jpelgrom]

Summary

Add a QR code scanner to the app (home-assistant/frontend#19570). This uses the 'old' ZXing library because something like MLKit is not 100% open source and would exclude the minimal flavor.

This PR is in a draft state because the UI is feature complete and may be reviewed, but external bus integration still needs to be added. The scanner currently replaces Settings > Companion app to launch it.

Screenshots

Recreated from design in frontend PR and the Google Matter barcode scanner which closely matches the design sample

Active scanner	Active scanner, landscape optimized layout	Permission denied

Link to pull request in Documentation repository

n/a

Any other notes