Dashboard sparkline dated axis, full-width tiles, loading skeletons

What does this MR do?

Frontend polish for the AI Governance dashboard summary tiles (part of #610983), plus the "Audit trail" to "Audit logs" rename (#612367).

Summary tiles (#610983)

• Dated sparkline x-axis: re-adds bucketStart and maps the x-axis to the bucket date, so the tooltip shows a real date (for example "Aug 9") instead of a meaningless sequence index.
• Full-width tiles: the two tiles each take half the row (dropped the max-width cap).
• Loading skeletons: tiles show a skeleton while the metrics query loads.

Dashboard cards (#612367)

• Renamed the "Audit trail" card to "Audit logs" (card title, error text, and the "View all audit logs" link) to match #612367.
• Reordered the two cards so "AI agent inventory" comes first and "Audit logs" second.

Screenshot

Before	After

Follow-up

The design's "running total at a point in time" needs a backend cumulative metric: trend returns per-day counts, and the agents KPI is a distinct count that cannot be summed client-side. Proposed in #616814.