Fix incorrect contract filename in fallback handler tutorial

[Dev M (devtechedge)]

Summary

• The fallback handler tutorial told readers to create NoDelegatecallGuard.sol, which is left over from the guards tutorial.
• Renamed that setup step to ERC1271FallbackHandler.sol so it matches the contract and tests in the rest of the page.

Fixes #826

Test plan

• Open the smart account fallback handler tutorial and confirm the "Create a new Solidity contract" step names ERC1271FallbackHandler.sol
• Spot-check that later code samples still use ERC1271FallbackHandler

[Daniel (dasanra)]

Dev M (@devtechedge) could you please sign your commit?

Thank you

[Dev M (devtechedge)]

Done — the commit is now signed off with Signed-off-by: devtechedge <devtechedge@users.noreply.github.com> (updated in 4549b69, force-pushed).

[Daniel (dasanra)]

Hey Dev M (@devtechedge) this is what we refer to when signing commits:

https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits

Sorry for the confusion

[Dev M (devtechedge)]

Thanks for the clarification, and no worries at all.

I have reworked the commit to be cryptographically signed with my SSH key, following the GitHub docs you linked. The latest commit (a5b479d) now shows as Verified on GitHub, and it also keeps the Signed-off-by trailer from the earlier change, so both the signature and the DCO check are covered.

Let me know if anything else is needed on this PR. Thanks for the review.

[Dev M (devtechedge)]

Thanks for the approval, Daniel (@dasanra).

Both red checks fail for a reason that has nothing to do with this diff.

Report readability and Deploy to staging each post a PR comment using GITHUB_TOKEN, which GitHub downgrades to read-only for fork pull requests, so both jobs end with Resource not accessible by integration (HTTP 403) before they look at any content.

The two checks that only need contents: read (markdown-link-check and vale-docs) are green, and the same two jobs pass on #903 and the dependabot PRs, which were opened from branches inside this repo.

Nothing changed after your review of a5b479d, so the branch is still exactly what you approved.