Sales Dashboard grid sample implementation

[dkamburov]

Implement a Sales Dashboard grid sample matching the design from Sales sample in webcomponents.

Design reference:

• Pivot grid for trend analysis, KPIs, and viewing sales summaries by region, product and other breakdowns.
• Key features: drag/drop pivoting, aggregation (sum, count), KPI visualizations (bar/column in-cells), dynamic data updates.
• Responsive panel with configuration for columns, rows, values, filters, similar to referenced design.
• Styled according to Indigo/Light theme.
• Sample Design (WebComponents)

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• Theme: Indigo
• Mode: Light
• See also WebComponents repo for base implementation.