Feature/v20/decouple kpi and proportional widget view

[erzik987]

Frontend Pull Request Description

Extracts KPI tile and proportional chart rendering into standalone view components that work without Pizzagna framework dependencies (no PIZZAGNA_EVENT_BUS, DATA_SOURCE, or providers required).

What's new
KpiTileViewComponent — standalone KPI tile with configurable value, label, colors, loading state, and interaction
ProportionalChartViewComponent — standalone proportional chart (donut/pie/bar) with legend placement options
NuiDashboardViewsModule — new module exporting both components
Unit tests and documentation examples for both components
Refactoring
KpiComponent now delegates rendering to nui-kpi-tile-view internally (no breaking changes)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have updated change log
• I have been following Definition of done
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new lint warnings
• New and existing unit tests pass locally and on CI with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

Additional Context (if necessary)