fix(docs): Correct README clone URL and directory to circlefin/arc-nanopayments

[Sertug17]

Summary

The README's "Getting Started" section references both an internal repository name and a stale directory name in the clone command, which returns 404 for new contributors:

git clone https://github.com/akelani-circle/arc-nanopayments-demo.git
cd arc-nanopayments-demo

The correct public repository is circlefin/arc-nanopayments and the cd path should match. This blocks the entire setup flow on the very first step.

Change

-git clone https://github.com/akelani-circle/arc-nanopayments-demo.git
-cd arc-nanopayments-demo
+git clone https://github.com/circlefin/arc-nanopayments.git
+cd arc-nanopayments

Verification

$ git ls-remote https://github.com/akelani-circle/arc-nanopayments-demo.git
ERROR: Repository not found.

$ git ls-remote https://github.com/circlefin/arc-nanopayments.git
✅ resolves

Related

The same akelani-circle/... pattern was identified across other Arc sample apps and addressed in:

• arc-fintech#9 by @skyc1e
• arc-escrow#16 by me
• arc-p2p-payments#9 by me

This PR completes the same minimal fix across the public Arc sample app repositories.

Notes

• This is a documentation-only change (1 file, +2/-2).
• Note that this repo's case is slightly worse than the others both the org (akelani-circle → circlefin) and the repo name (arc-nanopayments-demo → arc-nanopayments) need correcting, hence the cd line also changes.