Is your feature request related to a problem? Please describe.

When using NcProgressBar, there is currently no way to display the numeric percentage value (e.g. 42%) alongside the visual progress indicator.

Relevant code reference:

• value is used only for progress calculation and ARIA
• No text output or slot exists to render the numeric value

Describe the solution you'd like

A minimal solution could be an optional prop (e.g. showValue) that renders the percentage as an overlay or label for the linear progress bar, without changing the default appearance for existing users.

Additional context

This issue is visible in nextcloud/tables and tracked there as well: nextcloud/tables#1885