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/popover.js

@@ -0,0 +1,29 @@
+import * as PopoverPrimitive from '@radix-ui/react-popover';
+import { cn } from '@/lib/utils';
+
+function Popover({ ...props }) {
+    return <PopoverPrimitive.Root data-slot="popover" {...props} />;
+}
+
+function PopoverTrigger({ ...props }) {
+    return <PopoverPrimitive.Trigger data-slot="popover-trigger" {...props} />;
+}
+
+function PopoverContent({ className, align = "center", sideOffset = 4, ...props }) {
+    return (
+        <PopoverPrimitive.Portal>
+            <PopoverPrimitive.Content
+                data-slot="popover-content"
+                align={align}
+                sideOffset={sideOffset}
+                className={cn(
+                    "z-50 w-72 rounded-md border bg-popover p-4 text-popover-foreground shadow-md outline-none data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
+                    className
+                )}
+                {...props}
+            />
+        </PopoverPrimitive.Portal>
+    );
+}
+
+export { Popover, PopoverTrigger, PopoverContent };