phsl / new-api

* Re-architected model-pricing page into modular components:
  * PricingPage / PricingSidebar / PricingContent
  * Removed obsolete `ModelPricing*` components and column defs
* Introduced reusable `SelectableButtonGroup` in `common/ui`
  * Supports Row/Col grid (3 per row)
  * Optional collapsible mode with gradient mask & toggle
* Rebuilt filter panels with the new button-group:
  * Model categories, token groups, and quota types
  * Added dynamic `tagCount` badges to display item totals
* Extended `useModelPricingData` hook
  * Added `filterGroup` and `filterQuotaType` state and logic
* Updated PricingTable columns & sidebar reset logic to respect new states
* Ensured backward compatibility via re-export in `index.jsx`
* Polished styling, icons and i18n keys