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/button.tsx

@@ -1,52 +1,64 @@
-"use client"
+import * as React from 'react'
+import { Button as MantineButton } from '@mantine/core'
 
-import { Button as ButtonPrimitive } from "@base-ui/react/button"
-import { cva, type VariantProps } from "class-variance-authority"
-import { cn } from "../core/cn"
+type ButtonVariant = 'default' | 'outline' | 'secondary' | 'ghost' | 'destructive' | 'link'
+type ButtonSize = 'default' | 'xs' | 'sm' | 'lg' | 'icon' | 'icon-xs' | 'icon-sm' | 'icon-lg'
 
-const buttonVariants = cva(
-  "group/button inline-flex shrink-0 items-center justify-center rounded-lg border border-transparent bg-clip-padding text-sm font-medium whitespace-nowrap transition-all outline-none select-none focus-visible:border-ring focus-visible:ring-3 focus-visible:ring-ring/50 active:translate-y-px disabled:pointer-events-none disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-3 aria-invalid:ring-destructive/20 dark:aria-invalid:border-destructive/50 dark:aria-invalid:ring-destructive/40 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
-  {
-    variants: {
-      variant: {
-        default: "bg-primary text-primary-foreground [a]:hover:bg-primary/80",
-        outline: "border-border bg-background hover:bg-muted hover:text-foreground aria-expanded:bg-muted aria-expanded:text-foreground dark:border-input dark:bg-input/30 dark:hover:bg-input/50",
-        secondary: "bg-secondary text-secondary-foreground hover:bg-secondary/80 aria-expanded:bg-secondary aria-expanded:text-secondary-foreground",
-        ghost: "hover:bg-muted hover:text-foreground aria-expanded:bg-muted aria-expanded:text-foreground dark:hover:bg-muted/50",
-        destructive: "bg-destructive/10 text-destructive hover:bg-destructive/20 focus-visible:border-destructive/40 focus-visible:ring-destructive/20 dark:bg-destructive/20 dark:hover:bg-destructive/30 dark:focus-visible:ring-destructive/40",
-        link: "text-primary underline-offset-4 hover:underline",
-      },
-      size: {
-        default: "h-8 gap-1.5 px-2.5 has-data-[icon=inline-end]:pr-2 has-data-[icon=inline-start]:pl-2",
-        xs: "h-6 gap-1 rounded-[min(var(--radius-md),10px)] px-2 text-xs",
-        sm: "h-7 gap-1 rounded-[min(var(--radius-md),12px)] px-2.5 text-[0.8rem]",
-        lg: "h-9 gap-1.5 px-2.5 has-data-[icon=inline-end]:pr-3 has-data-[icon=inline-start]:pl-3",
-        icon: "size-8",
-        "icon-xs": "size-6 rounded-[min(var(--radius-md),10px)]",
-        "icon-sm": "size-7 rounded-[min(var(--radius-md),12px)]",
-        "icon-lg": "size-9",
-      },
-    },
-    defaultVariants: {
-      variant: "default",
-      size: "default",
-    },
-  }
-)
+const variantMap: Record<ButtonVariant, { variant: string; color?: string }> = {
+  default: { variant: 'filled' },
+  outline: { variant: 'outline' },
+  secondary: { variant: 'light' },
+  ghost: { variant: 'subtle' },
+  destructive: { variant: 'filled', color: 'red' },
+  link: { variant: 'transparent' },
+}
+
+const sizeMap: Record<ButtonSize, { size: string; style?: React.CSSProperties }> = {
+  default: { size: 'sm' },
+  xs: { size: 'xs' },
+  sm: { size: 'xs' },
+  lg: { size: 'md' },
+  icon: { size: 'sm', style: { width: 32, height: 32, padding: 0 } },
+  'icon-xs': { size: 'xs', style: { width: 24, height: 24, padding: 0 } },
+  'icon-sm': { size: 'xs', style: { width: 28, height: 28, padding: 0 } },
+  'icon-lg': { size: 'md', style: { width: 36, height: 36, padding: 0 } },
+}
+
+/** Kept for backwards compatibility — maps variant names to Mantine equivalents */
+const buttonVariants = variantMap
+
+interface ButtonProps extends React.ComponentPropsWithoutRef<'button'> {
+  variant?: ButtonVariant
+  size?: ButtonSize
+  children?: React.ReactNode
+}
 
 function Button({
   className,
-  variant = "default",
-  size = "default",
+  variant = 'default',
+  size = 'default',
+  style,
+  children,
   ...props
-}: ButtonPrimitive.Props & VariantProps<typeof buttonVariants>) {
+}: ButtonProps) {
+  const mv = variantMap[variant]
+  const ms = sizeMap[size]
+
   return (
-    <ButtonPrimitive
+    <MantineButton
       data-slot="button"
-      className={cn(buttonVariants({ variant, size, className }))}
+      variant={mv.variant}
+      color={mv.color}
+      size={ms.size}
+      radius="md"
+      className={className}
+      style={{ ...ms.style, ...style }}
       {...props}
-    />
+    >
+      {children}
+    </MantineButton>
   )
 }
 
 export { Button, buttonVariants }
+export type { ButtonProps, ButtonVariant, ButtonSize }