Dashboard previews now match shared links

Fixed

• Dashboard artifact previews now load from BinHTML's secure preview route instead of a browser-only preview copy.
• Uploaded HTML that works from a shared link should now look the same when viewed from the artifact detail page.
• Relative assets in generated reports, prototypes, and dashboards are handled more consistently in dashboard previews.

Improved

• The dashboard no longer sends the full HTML source through the artifact detail page just to show a preview.
• Preview behavior is now aligned across artifact cards, project cards, artifact detail pages, and shared links.

Why it matters

When you upload HTML, the dashboard preview should be a trustworthy reflection of what collaborators see from the share link. This fix removes a dashboard-only rendering difference that could make an artifact look broken even when the shared link worked correctly.