🎨 Palette: Add platform ambient shadows to KPI cards in reports

[kourdroid]

What: Added platform-specific ambient shadows to the kpiCard components on the Admin Reports page.
Why: The kpiCard items were previously completely flat on the Reports page, breaking the system's defined three-tier elevation model which requires a light platform shadow (shadowOpacity: 0.04, elevation: 2) to distinguish them from the canvas. This aligns them with the kpiCard rendering on the Director Dashboard.
Before/After: The flat kpiCards on the Reports screen now feature the subtle, standard elevation shadow.
Polish: This small refinement brings the reporting interface into strict consistency with the DESIGN.md rules and the rest of the app's components without any structural layout changes.

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PR created automatically by Jules for task 9852245802248760763 started by @kourdroid

[google-labs-jules]

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