fix(vite): Skip SSR middleware in preview server for SPA mode

[andreiborza]

When ssr: false is configured, the build removes the server bundle but configurePreviewServer was attempting to import it, causing "Cannot find module" errors when using vite preview.

Now skips SSR handling when SSR is disabled, allowing vite preview to work correctly in SPA mode.

Closes: #14672

---

Test demonstrating the issue: 8724df0
Fix for the issue: 37189ba

[changeset-bot]

🦋 Changeset detected

Latest commit: cb861b1

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

This PR includes changesets to release 11 packages

Name	Type
@react-router/dev	Patch
@react-router/fs-routes	Patch
@react-router/remix-routes-option-adapter	Patch
create-react-router	Patch
react-router	Patch
react-router-dom	Patch
@react-router/architect	Patch
@react-router/cloudflare	Patch
@react-router/express	Patch
@react-router/node	Patch
@react-router/serve	Patch

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[remix-cla-bot]

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[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

[github-actions]

🤖 Hello there,

We just published version 7.12.0-pre.0 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

[github-actions]

🤖 Hello there,

We just published version 7.12.0 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!