Refactor frontend structure and update dependencies

- Changed the main entry point from main.jsx to main.tsx for TypeScript support.
- Removed Tabler JS import and integrated Tailwind CSS for styling.
- Updated package.json and package-lock.json to include new dependencies such as @fontsource-variable/geist and tailwindcss, while removing unused ones.
- Enhanced Vite configuration with path aliasing for improved import management.
- Deleted unused App.css and App.jsx files to streamline the project structure.

Made-with: Cursor

frontend/src/components/ui/skeleton.tsx

@@ -0,0 +1,13 @@
+import { cn } from "@/lib/utils"
+
+function Skeleton({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="skeleton"
+      className={cn("animate-pulse rounded-md bg-muted", className)}
+      {...props}
+    />
+  )
+}
+
+export { Skeleton }