UI foundations: PageHeader, StatTile, validated chart palette, registry primitives

- PageHeader + StatTile standardize the four header and three stat-tile
  variants found in the audit; Inicio and Salarios migrated as proof.
- chart tokens replaced with a teal-anchored categorical scale, CVD-
  ordered and validated (six checks, light + dark surfaces).
- Registry adds: empty, field, item, spinner, progress, toggle-group,
  input-group, popover, kbd (+ toggle dep).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/ui/empty.tsx

@@ -0,0 +1,104 @@
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+function Empty({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="empty"
+      className={cn(
+        "flex w-full min-w-0 flex-1 flex-col items-center justify-center gap-4 rounded-xl border-dashed p-6 text-center text-balance",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function EmptyHeader({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="empty-header"
+      className={cn("flex max-w-sm flex-col items-center gap-2", className)}
+      {...props}
+    />
+  )
+}
+
+const emptyMediaVariants = cva(
+  "mb-2 flex shrink-0 items-center justify-center [&_svg]:pointer-events-none [&_svg]:shrink-0",
+  {
+    variants: {
+      variant: {
+        default: "bg-transparent",
+        icon: "flex size-8 shrink-0 items-center justify-center rounded-lg bg-muted text-foreground [&_svg:not([class*='size-'])]:size-4",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+    },
+  }
+)
+
+function EmptyMedia({
+  className,
+  variant = "default",
+  ...props
+}: React.ComponentProps<"div"> & VariantProps<typeof emptyMediaVariants>) {
+  return (
+    <div
+      data-slot="empty-icon"
+      data-variant={variant}
+      className={cn(emptyMediaVariants({ variant, className }))}
+      {...props}
+    />
+  )
+}
+
+function EmptyTitle({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="empty-title"
+      className={cn(
+        "font-heading text-sm font-medium tracking-tight",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function EmptyDescription({ className, ...props }: React.ComponentProps<"p">) {
+  return (
+    <div
+      data-slot="empty-description"
+      className={cn(
+        "text-sm/relaxed text-muted-foreground [&>a]:underline [&>a]:underline-offset-4 [&>a:hover]:text-primary",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function EmptyContent({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="empty-content"
+      className={cn(
+        "flex w-full max-w-sm min-w-0 flex-col items-center gap-2.5 text-sm text-balance",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export {
+  Empty,
+  EmptyHeader,
+  EmptyTitle,
+  EmptyDescription,
+  EmptyContent,
+  EmptyMedia,
+}