refactor: migrate frontend from shadcn/Tailwind to Mantine v9

Reescribe todos los componentes UI para usar Mantine v9 en lugar de shadcn/Tailwind.
Elimina cn(), CVA, components.json, theme_provider custom y globals.css con Tailwind.
Añade 25+ componentes nuevos (AppShell, AuthForm, DatePickerInput, Dropzone, etc.)
y MantineProvider como wrapper estándar del sistema de temas.

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

frontend/functions/ui/card.tsx

@@ -1,89 +1,99 @@
-import * as React from "react"
-import { cn } from "../core/cn"
+import * as React from 'react'
+import { Paper, Box, Text } from '@mantine/core'
 
-type CardVariant = "default" | "borderless" | "ghost"
+type CardVariant = 'default' | 'borderless' | 'ghost'
 
 function Card({
   className,
-  size = "default",
-  variant = "default",
+  size = 'default',
+  variant = 'default',
+  children,
   ...props
-}: React.ComponentProps<"div"> & { size?: "default" | "sm"; variant?: CardVariant }) {
+}: React.ComponentProps<'div'> & { size?: 'default' | 'sm'; variant?: CardVariant }) {
   return (
-    <div
+    <Paper
       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 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
-      )}
+      withBorder={variant === 'default'}
+      shadow={variant === 'default' ? 'xs' : undefined}
+      radius="md"
+      p={size === 'sm' ? 'sm' : 'md'}
+      bg={variant === 'ghost' ? 'transparent' : undefined}
+      className={className}
       {...props}
-    />
+    >
+      {children}
+    </Paper>
   )
 }
 
-function CardHeader({ className, ...props }: React.ComponentProps<"div">) {
+function CardHeader({ className, ...props }: React.ComponentProps<'div'>) {
   return (
-    <div
+    <Box
       data-slot="card-header"
-      className={cn(
-        "group/card-header @container/card-header grid auto-rows-min items-start gap-1 rounded-t-xl px-4 group-data-[size=sm]/card:px-3 has-data-[slot=card-action]:grid-cols-[1fr_auto] has-data-[slot=card-description]:grid-rows-[auto_auto] [.border-b]:pb-4 group-data-[size=sm]/card:[.border-b]:pb-3",
-        className
-      )}
+      pb="xs"
+      className={className}
       {...props}
     />
   )
 }
 
-function CardTitle({ className, ...props }: React.ComponentProps<"div">) {
+function CardTitle({ className, ...props }: React.ComponentProps<'div'>) {
   return (
-    <div
+    <Text
+      component="div"
       data-slot="card-title"
-      className={cn("text-base leading-snug font-medium group-data-[size=sm]/card:text-sm", className)}
+      fw={600}
+      size="sm"
+      className={className}
       {...props}
     />
   )
 }
 
-function CardDescription({ className, ...props }: React.ComponentProps<"div">) {
+function CardDescription({ className, ...props }: React.ComponentProps<'div'>) {
   return (
-    <div
+    <Text
+      component="div"
       data-slot="card-description"
-      className={cn("text-sm text-muted-foreground", className)}
+      size="sm"
+      c="dimmed"
+      className={className}
       {...props}
     />
   )
 }
 
-function CardAction({ className, ...props }: React.ComponentProps<"div">) {
+function CardAction({ className, style, ...props }: React.ComponentProps<'div'>) {
   return (
-    <div
+    <Box
       data-slot="card-action"
-      className={cn("col-start-2 row-span-2 row-start-1 self-start justify-self-end", className)}
+      style={{ position: 'absolute', top: 0, right: 0, ...style }}
+      className={className}
       {...props}
     />
   )
 }
 
-function CardContent({ className, ...props }: React.ComponentProps<"div">) {
+function CardContent({ className, ...props }: React.ComponentProps<'div'>) {
   return (
-    <div
+    <Box
       data-slot="card-content"
-      className={cn("px-4 group-data-[size=sm]/card:px-3", className)}
+      className={className}
       {...props}
     />
   )
 }
 
-function CardFooter({ className, ...props }: React.ComponentProps<"div">) {
+function CardFooter({ className, ...props }: React.ComponentProps<'div'>) {
   return (
-    <div
+    <Box
       data-slot="card-footer"
-      className={cn("flex items-center rounded-b-xl border-t bg-muted/50 p-4 group-data-[size=sm]/card:p-3", className)}
+      pt="sm"
+      mt="auto"
+      style={{ borderTop: '1px solid var(--mantine-color-default-border)' }}
+      className={className}
       {...props}
     />
   )