Update NFT media CORS validation

[JOY (JOY)]

Description and Related Issue(s)

Update the Vietnamese NFT Media Handler report after the Metadata Service CORS regression was fixed and deployed by DOS/DOScan#122.

Proposed Changes

• Record backend PR fix link to transactions blockscout/frontend#122 and deployment workflow #30343254663.
• Add separate evidence for the same-origin proxy workflow checks and the post-deploy Playwright verification on the Testnet NFT page.
• Link the exact NFT instance used for the browser validation.

No environment variable definitions are changed in this PR.

Breaking or Incompatible Changes

None.

Additional Information

The self-contained HTML report was rendered through a local HTTP server and visually checked in dark mode. An independent reviewer approved the final diff. The repository Husky hook could not start because .husky/_/husky.sh is absent in this worktree, so the docs-only commit used --no-verify after git diff --check and character validation passed.

Checklist for PR author

• I have tested these changes locally.
• I added tests to cover any new functionality, following this guide.
• Whenever I fix a bug, I include a regression test to ensure that the bug does not reappear silently.
• If I have added a feature or functionality that is not privacy-compliant, I have disabled it for private mode. Not applicable to this documentation-only change.
• If I have added, changed, renamed, or removed an environment variable. Not applicable, no environment variable definition changed.