feat(ui): make dashboard responsive for iPhone and mobile devices

- Add Sheet primitive component for mobile drawers
- Add MobileNav with hamburger menu for dashboard layout
- Hide desktop sidebars on mobile; show mobile header
- Make dashboard header responsive with stacked layout on small screens
- Hide selector text on mobile, show icons only
- Convert fixed-width filters to responsive widths (CFDI, Clientes, Admin, Documentos, Alertas)
- Cap dialog widths to 95vw on mobile (CFDI viewer, Documentos, Reportes, Contribuyentes, Facturación)
- Make calendar grid smaller and use single-letter weekdays on mobile
- Update viewport to include viewport-fit=cover for Samsung safe areas

apps/web/components/contribuyente-selector.tsx

@@ -52,10 +52,10 @@ export function ContribuyenteSelector() {
     <div className="contribuyente-selector relative">
       <button
         onClick={() => setOpen(!open)}
-        className="flex items-center gap-2 rounded-lg px-3 py-2 text-sm font-medium hover:bg-accent transition-colors"
+        className="flex items-center gap-2 rounded-lg px-2 py-2 text-sm font-medium hover:bg-accent transition-colors sm:px-3"
       >
         <Building2 className="h-4 w-4" />
-        <span className="max-w-[180px] truncate">
+        <span className="hidden max-w-[180px] truncate sm:inline">
           {selected ? selected.nombre : 'Todos los RFCs'}
         </span>
         <ChevronDown className={cn('h-4 w-4 transition-transform', open && 'rotate-180')} />