feat: nuevos componentes UI — accordion, avatar, breadcrumb, checkbox, command, dropdown, pagination, popover, radio, sheet, select, switch, textarea, toast

Componentes React accesibles basados en Radix UI con soporte de temas via CSS variables. Incluye barrel export en index.ts.

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

frontend/functions/ui/pagination.md

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+---
+name: pagination
+kind: component
+lang: ts
+domain: ui
+version: "1.0.0"
+purity: impure
+signature: "Pagination(props: PaginationProps): JSX.Element"
+description: "Controles de navegacion de paginas con Previous/Next, numeros de pagina, elipsis y estado activo."
+tags: [pagination, navigation, component, ui]
+uses_functions: [cn_ts_core]
+uses_types: []
+returns: []
+returns_optional: false
+error_type: ""
+imports: ["lucide-react", "./button"]
+tested: false
+tests: []
+test_file_path: ""
+file_path: "frontend/functions/ui/pagination.tsx"
+props:
+  - name: className
+    type: "string"
+    required: false
+    description: "Clases CSS adicionales"
+emits: []
+has_state: false
+framework: react
+variant: []
+---
+
+## Ejemplo
+
+```tsx
+<Pagination>
+  <PaginationContent>
+    <PaginationItem>
+      <PaginationPrevious href="/page/1" />
+    </PaginationItem>
+    <PaginationItem>
+      <PaginationLink href="/page/1">1</PaginationLink>
+    </PaginationItem>
+    <PaginationItem>
+      <PaginationLink href="/page/2" isActive>2</PaginationLink>
+    </PaginationItem>
+    <PaginationItem>
+      <PaginationLink href="/page/3">3</PaginationLink>
+    </PaginationItem>
+    <PaginationItem>
+      <PaginationEllipsis />
+    </PaginationItem>
+    <PaginationItem>
+      <PaginationNext href="/page/3" />
+    </PaginationItem>
+  </PaginationContent>
+</Pagination>
+```
+
+## Notas
+
+Exports: Pagination (nav), PaginationContent (ul), PaginationItem (li), PaginationLink (a con isActive/disabled), PaginationPrevious, PaginationNext, PaginationEllipsis. PaginationLink reutiliza buttonVariants para consistencia visual. Componente presentacional — el manejo del estado de pagina queda en el consumidor.