[eas-cli] Remove Express from image URL test

[sjchmiela]

Why

The image URL test only needs to serve a single PNG over HTTP. Using Express for that adds an otherwise-unused framework and its dependency tree to EAS CLI test dependencies.

This supersedes #3969. That PR upgrades Express to address the vulnerable transitive path-to-regexp version, but after this change EAS CLI no longer depends on Express, so the affected dependency path is removed instead of upgraded.

What changed

• replace the Express static server with Node's built-in http server
• bind to port 0 so the operating system selects an available port
• remove express and @types/express from packages/eas-cli
• regenerate the lockfile, removing the associated Express 4 dependency tree

Impact

This only changes test infrastructure. The test continues to exercise the real remote-URL fetch and PNG transparency validation path. There is no EAS CLI runtime behavior change.

Validation

• yarn workspace eas-cli test src/utils/__tests__/image-test.ts --runInBand
• yarn workspace eas-cli typecheck
• formatting check
• git diff --check

[github-actions]

⏩ The changelog entry check has been skipped since the "no changelog" label is present.

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.67%. Comparing base (4b1f785) to head (bf275da).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4008   +/-   ##
=======================================
  Coverage   59.67%   59.67%           
=======================================
  Files         941      941           
  Lines       41319    41319           
  Branches     8675     8675           
=======================================
  Hits        24654    24654           
  Misses      16571    16571           
  Partials       94       94           

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