Remove unused files and dependencies with Knip

[zetter-rpf]

This uses the Knip tool to remove unused code and dependencies, similar to https://github.com/RaspberryPiFoundation/editor-standalone/pull/770.

It seems that most removals are due to:

• Code that was copied when this project was split from editor-standalone that was never used
• Packages that are no longer needed as dependencies as we don't directly use them (but they may be still installed as dependencies of dependencies)
• Packages that were installed by default as part of the ejecting of 'create react app'.

I've tested the build locally from classroom and editor and all project types are working as expected.

This takes us from around 2540 dependencies (170 direct) to 2264 (132 direct), although doesn't change the build size that much as the dependencies were unused.

[Copilot]

Pull request overview

Cleans up the editor-ui codebase by removing unused source files, styles, build helpers, and dependencies identified via Knip (primarily legacy CRA/ejected-Cra artifacts and unused code carried over from editor-standalone).

Changes:

• Removed unused runtime/dev dependencies and updated yarn.lock accordingly.
• Deleted unused application/util/redux files and unused SCSS stylesheets.
• Simplified some module exports (Redux slices, components, Cypress helpers) to reflect actual usage.

Reviewed changes

Copilot reviewed 26 out of 27 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
yarn.lock	Lockfile updated to reflect dependency removals/additions.
package.json	Removed unused deps/devDeps; added TypeScript-related dev tooling deps.
src/utils/sentry.js	Removed unused Sentry initialization module.
src/utils/reportWebVitals.js	Removed unused web-vitals reporting helper.
src/utils/defaultProjects.js	Removed unused HTML default project helpers/exports; retained Python defaults.
src/redux/WebComponentSlice.js	Removed unused Redux slice.
src/redux/WebComponentAuthSlice.js	Adjusted slice visibility/exports to only expose used actions.
src/redux/InstructionsSlice.js	Adjusted slice visibility/export style without changing reducer behavior.
src/redux/EditorSlice.js	Adjusted slice visibility and pruned exported actions list to those in use.
src/hooks/useUserFont.js	Removed unused hook.
src/hooks/useRequiresUser.js	Removed unused hook.
src/components/Menus/Sidebar/DownloadPanel/DownloadPanel.jsx	Switched to internal const component while keeping default export.
src/components/Editor/NewInputPanelButton/NewInputPanelButton.jsx	Removed unused component.
src/assets/stylesheets/rpf_design_system/typography.scss	Removed unused stylesheet.
src/assets/stylesheets/ProjectListTable.scss	Removed unused stylesheet.
src/assets/stylesheets/ProjectListItem.scss	Removed unused stylesheet.
src/assets/stylesheets/ProjectIndexPagination.scss	Removed unused stylesheet.
src/assets/stylesheets/ProjectIndexHeader.scss	Removed unused stylesheet.
src/assets/stylesheets/LoginMenu.scss	Removed unused stylesheet.
src/assets/stylesheets/LandingPage.scss	Removed unused stylesheet.
cypress/helpers/scratch.js	Reduced exported helper surface to what’s used.
cypress/helpers/editor.js	Reduced exported helper surface and removed unused HTML-runner helper functions.
config/webpackDevServer.config.js	Removed unused CRA-derived dev-server config helper.
config/svgo.config.js	Removed unused SVGO config file.
config/pnpTs.js	Removed unused PnP TypeScript resolver helper.
config/modules.js	Removed unused CRA module-resolution helper.
config/getHttpsConfig.js	Removed unused CRA HTTPS config helper.

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[DNR500]

Looks good :-)