feat: mejoras componentes UI — card variants, kpi_card slots, sparkline colors, bar_chart horizontal radius

- card: variantes default/borderless/ghost con ring condicional
- kpi_card: props unit, action, chart y delta con label/suffix personalizable
- sparkline: prop colors para colores por barra en variant bar
- bar_chart: radius condicional según orientación horizontal/vertical

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/functions/ui/card.tsx

@@ -1,17 +1,24 @@
 import * as React from "react"
 import { cn } from "../core/cn"
 
+type CardVariant = "default" | "borderless" | "ghost"
+
 function Card({
   className,
   size = "default",
+  variant = "default",
   ...props
-}: React.ComponentProps<"div"> & { size?: "default" | "sm" }) {
+}: React.ComponentProps<"div"> & { size?: "default" | "sm"; variant?: CardVariant }) {
   return (
     <div
       data-slot="card"
       data-size={size}
+      data-variant={variant}
       className={cn(
-        "group/card flex flex-col gap-4 overflow-hidden rounded-xl bg-card py-4 text-sm text-card-foreground ring-1 ring-foreground/10 has-data-[slot=card-footer]:pb-0 has-[>img:first-child]:pt-0 data-[size=sm]:gap-3 data-[size=sm]:py-3 data-[size=sm]:has-data-[slot=card-footer]:pb-0 *:[img:first-child]:rounded-t-xl *:[img:last-child]:rounded-b-xl",
+        "group/card flex flex-col gap-4 overflow-hidden rounded-xl bg-card py-4 text-sm text-card-foreground has-data-[slot=card-footer]:pb-0 has-[>img:first-child]:pt-0 data-[size=sm]:gap-3 data-[size=sm]:py-3 data-[size=sm]:has-data-[slot=card-footer]:pb-0 *:[img:first-child]:rounded-t-xl *:[img:last-child]:rounded-b-xl",
+        variant === "default" && "ring-1 ring-foreground/10",
+        variant === "borderless" && "ring-0 shadow-none",
+        variant === "ghost" && "ring-0 shadow-none bg-transparent",
         className
       )}
       {...props}