feat: add shadcn/ui + Tailwind CSS v4 + Huge Icons foundation

- Install tailwindcss, @tailwindcss/postcss, clsx, tailwind-merge, class-variance-authority
- Install @hugeicons/react for icons
- Install Radix UI primitives (switch, tabs, label, separator, select, dialog, checkbox, dropdown-menu, popover)
- Install sonner for toast notifications
- Create postcss.config.js with Tailwind v4 PostCSS plugin
- Create jsconfig.json with @ path alias for src/admin
- Create components.json for shadcn configuration
- Update webpack.config.js with @ resolve alias
- Create globals.css with Tailwind v4 CSS-first config + shadcn CSS variables
- Create cn() utility in lib/utils.js
- Create 17 shadcn UI components (button, input, label, checkbox, switch, tabs, alert, separator, badge, textarea, dialog, sonner, table, skeleton, select, dropdown-menu, popover)
- Create async confirm() utility replacing SweetAlert2
- Create toast utility wrapping sonner

src/admin/components/ui/switch.js

@@ -0,0 +1,25 @@
+import * as SwitchPrimitive from '@radix-ui/react-switch';
+import { cn } from '@/lib/utils';
+
+function Switch({ className, checked, onCheckedChange, ...props }) {
+    return (
+        <SwitchPrimitive.Root
+            data-slot="switch"
+            checked={checked}
+            onCheckedChange={onCheckedChange}
+            className={cn(
+                "peer inline-flex h-5 w-9 shrink-0 cursor-pointer items-center rounded-full border-2 border-transparent shadow-sm transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background disabled:cursor-not-allowed disabled:opacity-50 data-[state=checked]:bg-primary data-[state=unchecked]:bg-input",
+                className
+            )}
+            {...props}
+        >
+            <SwitchPrimitive.Thumb
+                className={cn(
+                    "pointer-events-none block h-4 w-4 rounded-full bg-background shadow-lg ring-0 transition-transform data-[state=checked]:translate-x-4 data-[state=unchecked]:translate-x-0"
+                )}
+            />
+        </SwitchPrimitive.Root>
+    );
+}
+
+export { Switch };