Merge pull request #32761 from backstage/rugvip/css-exports-support

cli: add support for CSS exports in package build

.changeset/css-exports-support.md

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+---
+'@backstage/cli': patch
+---
+
+Added support for CSS exports in package builds. When a package declares a CSS file in its `exports` field (e.g., `"./styles.css": "./src/styles.css"`), the CLI will automatically bundle it during `backstage-cli package build`, resolving any `@import` statements. The export path is rewritten from `src/` to `dist/` at publish time.
+
+Fixed `backstage-cli repo fix` to not add `typesVersions` entries for non-script exports like CSS files.

.changeset/ui-standard-build.md

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+---
+'@backstage/ui': patch
+---
+
+Migrated to use the standard `backstage-cli package build` for CSS bundling instead of a custom build script.