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/ring_progress.tsx

@@ -0,0 +1,32 @@
+import * as React from 'react'
+import { RingProgress } from '@mantine/core'
+import type { RingProgressSection } from '@mantine/core'
+
+interface FnRingProgressProps {
+  sections: RingProgressSection[]
+  size?: number
+  thickness?: number
+  label?: React.ReactNode
+  rootColor?: string
+}
+
+function FnRingProgress({
+  sections,
+  size = 120,
+  thickness = 12,
+  label,
+  rootColor,
+}: FnRingProgressProps) {
+  return (
+    <RingProgress
+      sections={sections}
+      size={size}
+      thickness={thickness}
+      label={label}
+      rootColor={rootColor}
+    />
+  )
+}
+
+export { FnRingProgress }
+export type { FnRingProgressProps }