Vite: Don't rebase absolute url()s (tailwindlabs#15275)

Closes tailwindlabs#15269

This PR fixes an issue where our Vite extension was rebasing absolute
urls inside `@import`-ed files. We forgot to cover this when we
implemented the URL rebasing.

## Test Plan

We validated that this fixes the repro in tailwindlabs#15269:

<img width="851" alt="Screenshot 2024-12-02 at 18 07 35"
src="https://github.com/user-attachments/assets/3b2c2be3-1f73-469e-9f64-301c6b948b02">

Also added a unit test for this.

Co-authored-by: Jordan Pittman <jordan@cryptica.me>

Author: philipp-spiess

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Ensure absolute `url()`s inside imported CSS files are not rebased when using `@tailwindcss/vite`
+
 ### Added
 
 - Parallelize parsing of individual source files ([#15270](https://github.com/tailwindlabs/tailwindcss/pull/15270))

packages/@tailwindcss-node/src/urls.ts

@@ -51,6 +51,8 @@ export async function rewriteUrls({
   let promises: Promise<void>[] = []
 
   function replacerForDeclaration(url: string) {
+    if (url[0] === '/') return url
+
     let absoluteUrl = path.posix.join(normalizePath(base), url)
     let relativeUrl = path.posix.relative(normalizePath(root), absoluteUrl)