Add QR code capture (#6705)

Select a screen region and decode the QR code in it to the clipboard, so
an otpauth:// setup code shown on screen no longer needs a phone.

The decoded value is only ever placed on the clipboard, and marked
sensitive so clipboard history skips it. Decoding is restricted to QR so
a stray barcode elsewhere on screen can't take the clipboard instead.

Co-authored-by: Hlib Kanunnikov <hlibwondertan@gmail.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

install/omarchy-base.packages

@@ -146,4 +146,5 @@ xournalpp
 yaru-icon-theme
 yay
 yt-dlp
+zbar
 zoxide