feat: apply CSS transformation for inlined CSS in Node bundles

[chenjiahan]

Summary

This change enables postcss-loader and lightningcss-loader for .css?inline files when building Node bundles.

Previously, CSS transformations only applied to web bundles, but .css?inline is also valid in SSR builds. Applying CSS transformation on the server side ensures that inline CSS content is processed consistently between Web and Node bundles, preventing mismatches during SSR hydration.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR enables CSS transformation (postcss-loader and lightningcss-loader) for .css?inline imports in Node bundles. Previously, these transformations only applied to web bundles, but inline CSS is also used in SSR scenarios where consistent transformation between client and server is critical for hydration.

• Modified the updateRules helper to conditionally skip normal CSS rules when emitCss is disabled
• Applied lightningcss-loader and postcss-loader to inline CSS rules regardless of target environment
• Updated importLoaders count for css-loader configuration

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

File	Description
packages/core/src/plugins/css.ts	Added skipNormal option to updateRules helper and applied lightningcss/postcss loaders to inline CSS rules even when emitCss is false
packages/core/tests/snapshots/*.snap	Updated test snapshots to reflect new loader configuration with increased importLoaders count and lightningcss-loader added to inline CSS rules
e2e/cases/css/inline-query-node-target/*	Added new e2e test to verify CSS transformation for inline imports with Node target in both dev and build modes

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[Copilot]

The importLoaders count is incremented unconditionally but the loader is only added to the inline rule when emitCss is false (via skipNormal: !emitCss). This results in the normal CSS rule having an incorrect importLoaders count. While this doesn't cause issues since the CSS is ignored via ignoreCssLoader, consider tracking separate counts for normal and inline rules or only incrementing when the loader applies to both rules for better code clarity.