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/data_table.md

@@ -8,12 +8,12 @@ purity: impure
 signature: "DataTable(props: DataTableProps): JSX.Element"
 description: "Tabla de datos con sticky header, overflow scroll, heatmap por columna, formato condicional (number/datetime/currency) y hover rows. Auto-detecta columnas desde la primera fila si no se proveen."
 tags: [table, data, heatmap, dashboard, component, ui, format, visualization]
-uses_functions: [cn_ts_core]
+uses_functions: []
 uses_types: []
 returns: []
 returns_optional: false
 error_type: ""
-imports: [react]
+imports: [react, "@mantine/core"]
 output: "Componente DataTable que renderiza tabla con sticky header, heatmap condicional y formato automático de datos"
 tested: false
 tests: []
@@ -44,10 +44,6 @@ props:
     type: "Error | null"
     required: false
     description: "Error a mostrar si la carga falló."
-  - name: className
-    type: "string"
-    required: false
-    description: "Clases CSS adicionales."
 emits: []
 has_state: false
 framework: react