feat: added progress indicator component

[giuliana-gladeye]

This feature branch includes work for ticket "Progress Indicator Component"

Added ProgressIndicator / ProgressIndicatorStep for showing position in a multi-step flow (e.g. policy creation), following Carbon's conventions.

ProgressIndicator: renders a full-length rail using our existing <Progress>, with the filled segment sized to one step and offset over currentIndex. layout="horizontal" (default) / "vertical" re-orients both rail and steps.

ProgressIndicatorStep: name, optional description, and status (editing / empty / neutral / success / info / danger) picks a lucide icon. Renders as <a> with href, <button> with onClick, otherwise a non interactive <div>.

Status colours: success/danger use badge colours, active step takes primary (matches MetricCard).

Docs: MDX with horizontal, vertical, onClick, and href examples, plus prop tables.

[Shrinks99]

Made a few changes, improved accessibility by making the container a nav if it has links / onclicks.

[giuliana-gladeye]

A few more updates:

• Added elevation prop to ProgressIndicator for Icon component.
• Fixed active sidebar link. Bug: /components/progress is a prefix of /components/progress-indicator, so startsWith matches both. Changed nav-list.astro isActive from startsWith to an exact match.