Sweep `akelani-circle/...` clone URL pattern across Arc sample app READMEs

[Sertug17]

Context

The same incorrect clone URL pattern (akelani-circle/<repo-name> instead
of circlefin/<repo-name>) appears in the README "Getting Started"
sections across multiple Arc sample apps. New contributors hit a 404
on the very first command of the setup flow.

Affected repos and current PR status

Repo	PR	Status
arc-fintech	#9 by @skyc1e	open
arc-escrow	#16 by me	open
arc-p2p-payments	#9 by me	open
arc-nanopayments	#13 by me	open

arc-nanopayments is the most severe case both the org and repo name
are wrong (akelani-circle/arc-nanopayments-demo), so contributors
hit two 404s in sequence.

Suggestion

This pattern looks like it originated from internal forks being
referenced before public release. A few thoughts to prevent recurrence
in future sample apps:

1. Pre-publish checklist verify all git clone commands in
   README resolve as part of the public release process.
2. CI check a simple grep in CI that fails if README contains
   akelani-circle/ or any non-circlefin/ org reference.
3. Template repo a starter template with placeholder <REPO_NAME>
   that gets substituted on creation.

Happy to help with any of the above if useful.

Why opening here

Opening this in arc-p2p-payments because it's the most actively
maintained sample app right now, but the pattern observation applies
across all four. Feel free to relocate or close if there's a more
appropriate place.