fix: Use URL parsing instead of substring matching in isExternal

[javascripter]

Summary

• Fix isExternal() to properly detect external URLs by parsing the URL and comparing the actual host, instead of using naive substring matching
• The previous url.includes(host) check incorrectly identified URLs as internal when the request host appeared anywhere in the URL string (path, query params, etc.)
• This broke rewrites to services like rendertron that embed the target URL in the path (e.g., https://rendertron.example.com/render/https://myapp.com/page)

Test plan

• Added unit tests for embedded URL cases
• Added unit tests for host:port matching
• All existing tests pass

I also applied this patch locally to our website (not public) to confirm that this fixes the bug mentioned in this PR.

URL	Request Host	Old Result	New Result
https://example.com/render/https://myapp.com/page	myapp.com	false ❌	true ✓

[changeset-bot]

🦋 Changeset detected

Latest commit: ff3c183

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@opennextjs/aws	Patch
app-pages-router	Patch

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[vicb]

LGTM, could you please add a patch changeset (via pnpm changeset)

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@opennextjs/aws@1046

commit: ff3c183

[vicb]

You also need to pnpm lint:fix to format the files before uploading the PR

[javascripter]

@vicb Thanks for reviewing! I've added the changeset and fixed linting errors.