Add license check to CI

[tom2drum]

Description and Related Issue(s)

Adds automated license compliance checking to CI so dependency licenses are validated on every run.

• Introduces license-report and license-report-check to generate a license report and fail the build when forbidden licenses (e.g. n/a) are present.
• Adds a "Check licenses" step to the code quality job in .github/workflows/checks.yml.
• Adds .license-reportrc to exclude @helia/verified-fetch (dual MIT/Apache-2.0 not recognized by the checker) and .gitignore entry for license.json.

Proposed Changes

• New devDependencies: license-report (6.8.1), license-report-check (0.1.2).
• New script: lint:license:check — runs license-report, then license-report-check with forbidden=n/a.
• CI: "Check licenses" step runs yarn lint:license:check in the code quality job.
• Config: .license-reportrc with exclude for @helia/verified-fetch; license.json added to .gitignore.

Breaking or Incompatible Changes

None.

Additional Information

N/A

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 (e.g., tracking, analytics, third-party services), I have disabled it for private mode.
• If I have added, changed, renamed, or removed an environment variable
  • I updated the list of environment variables in the documentation
  • I made the necessary changes to the validator script according to the guide
  • I added "ENVs" label to this pull request