feat: fallback schema lnurl

[abhiShandy]

• encodes the weburl and lnurl into the QR code
• Removes the button to switch between 2 QR codes since a single QR code is enough
• reduces the URL size by changing api/lnurlp to api/u
• Add LNURL Fallback Scheme to Web URL  #176
• DONE - Add LNURL Fallback Scheme to Web URL blink#1412

[UncleSamtoshi]

@abhiShandy Everything looks good here except the rename to the url needs to be reverted! The url path is part of the lnurl spec https://github.com/lnurl/luds/blob/38d8baa6f8e3b3dfd13649bfa79e2175d6ca42ff/16.md . It was a clever attempt at making the QR simpler though!

[abhiShandy]

Done!