Improve support for manual entry of QR codes when no webcam is available. #4

Problem: "Scan QR" code requires a webcam which some people disable and some hotel or library desktops don't have. This can make a compact codexQR backup impossible to recover until you get access to a computer with a webcam.

Proposed Solution: When no webcam is detected on the PC, change the "Scan QR Code" button to "Manual QR Code Entry"

Here it can present two methods of entry with the first preferred because it requires no additional device although it's slower than using an offline encrypted phone or tablet.

• Draw the QR code by clicking the tiles until it matches.
  • This can correct up to 14% errors and seems more intuitive and secure.
• Type the alphanumeric contents of the QR scanned by another trustworthy offline device.
  • This has some error detection even for compact codexQR but not as much.
  • 25 characters of base45 would need to be input.
  • This is much easier to implement than the manual QR drawing would be.