V15: Upload Field should use a better file preview

[iOvergaard]

Description

Fixes an issue where the serverUrl was shown twice and changes the component to use <uui-card-media /> instead.

Benefits include:

• better href
• no custom file symbols
• better a11y
• you can now see the filename

Screenshots

🔴 BEFORE

✅ AFTER

[Copilot]

Pull Request Overview

This PR improves the file preview in the upload field component by removing the duplicated server URL and replacing the previous preview with the component.

• Removed server URL concatenation and obsolete state properties
• Introduced private getters for label and file extension to drive the new card media component

Comments suppressed due to low confidence (1)

src/Umbraco.Web.UI.Client/src/packages/media/media/components/input-upload-field/preview/input-upload-field-file.element.ts:20

• The fallback logic in the getter for #label may yield an empty string when this.path is defined but does not contain a valid file name, potentially causing a missing label in the preview. Consider adding explicit handling for such edge cases.

return this.path.split('/').pop() ?? `(${this.localize.term('general_loading')}...)`;