Do not allow xApp opening in browser

[WietseWind]

Pathfinding is an xApp and should not open in the browser in the first place. Thing to fix here is that the xApp shouldn't allow for opening in the browser where no Xumm user agent is present. I'll add an issue on Github for when Koen is back from a few days off this week

[WietseWind]

https://monkdesk.xrpl-labs.com/agent/ticket/70513

[WietseWind]

Simply redirect to here: https://xumm.app/detect/xapp:xumm.pathfinding if no xumm in the user agent?