V16: Build Backoffice externals with Vite

[iOvergaard]

Description

The main purpose of this PR is to get rid of a direct dependency on Rollup, since Vite supports it out of the box. The src/externals/* are now considered workspaces with their package.json file and dependencies. Each package is built with Vite, which also makes it easier to use web workers (from monaco-editor) and different styling coming in from monaco, uui, and others.

Another change is that CSS is now being minified. Although it could be bundled with Vite, it isn't because we need to reference uui-css.css from the Login screen as well, and Vite inlines the whole Lato font, which does not work very well as the CSS files become very large.

Fixes AB#49259

[Copilot]

Pull Request Overview

This PR migrates the Umbraco backoffice external library builds from Rollup to Vite, replacing a complex Rollup configuration with individual Vite workspaces for each external library. This change simplifies dependency management, improves web worker support, and adds CSS minification.

• Replaces Rollup-based build system with Vite workspaces for external libraries
• Creates individual package.json files for each external library with their specific dependencies
• Improves Monaco Editor integration with proper web worker support using Vite's worker feature

Reviewed Changes

Copilot reviewed 27 out of 47 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Umbraco.Web.UI.Client/vite.config.ts	Removes Monaco Editor asset copying configuration
src/Umbraco.Web.UI.Client/src/vite-config-base.ts	Adds external parameter support and updates default external pattern
src/Umbraco.Web.UI.Client/src/rollup.config.js	Completely removes Rollup configuration file
src/Umbraco.Web.UI.Client/src/external/*/vite.config.ts	Adds Vite configuration for each external library workspace
src/Umbraco.Web.UI.Client/src/external/*/package.json	Creates workspace package.json with specific dependencies for each library
src/Umbraco.Web.UI.Client/src/external/monaco-editor/index.ts	Updates Monaco Editor to use Vite workers instead of URL-based workers
src/Umbraco.Web.UI.Client/package.json	Moves external dependencies to individual workspaces and removes Rollup dependencies
src/Umbraco.Web.UI.Client/devops/build/copy-to-cms.js	Adds asset copying and CSS minification steps

Files not reviewed (1)

• src/Umbraco.Web.UI.Client/package-lock.json: Language not supported

Comments suppressed due to low confidence (1)

src/Umbraco.Web.UI.Client/src/external/monaco-editor/index.ts:12

• [nitpick] The parameter name '_' should be more descriptive. Consider using 'workerId' to match the original function signature.

	getWorker(_, label) {

[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://victorious-ground-017b08103-19716.westeurope.6.azurestaticapps.net

[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://orange-sea-0c7411a03-19716.westeurope.6.azurestaticapps.net

[leekelleher]

Tested out with the various build setups: Vite, static and CMS build, all appear to be working as expected. 🚀