feat: add UI components including Skeleton, Slider, Toaster, Switch, Table, Tabs, Textarea, Toggle Group, Toggle, Tooltip, and User Avatar

- Implemented Skeleton component for loading states.
- Added Slider component using Radix UI for customizable sliders.
- Created Toaster component for notifications with theme support.
- Developed Switch component for toggle functionality.
- Introduced Table component with subcomponents for structured data display.
- Built Tabs component for tabbed navigation.
- Added Textarea component for multi-line text input.
- Implemented Toggle Group and Toggle components for grouped toggle buttons.
- Created Tooltip component for displaying additional information on hover.
- Added User Avatar component for displaying user images with fallback.
- Implemented useIsMobile hook for responsive design.
- Created API utility functions for user and thought data fetching.
- Added utility function for class name merging.
- Updated package.json with new dependencies for UI components and utilities.
- Added TypeScript configuration for path aliasing.

thoughts-frontend/components/ui/avatar.tsx

@@ -0,0 +1,53 @@
+"use client"
+
+import * as React from "react"
+import * as AvatarPrimitive from "@radix-ui/react-avatar"
+
+import { cn } from "@/lib/utils"
+
+function Avatar({
+  className,
+  ...props
+}: React.ComponentProps<typeof AvatarPrimitive.Root>) {
+  return (
+    <AvatarPrimitive.Root
+      data-slot="avatar"
+      className={cn(
+        "relative flex size-8 shrink-0 overflow-hidden rounded-full",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function AvatarImage({
+  className,
+  ...props
+}: React.ComponentProps<typeof AvatarPrimitive.Image>) {
+  return (
+    <AvatarPrimitive.Image
+      data-slot="avatar-image"
+      className={cn("aspect-square size-full", className)}
+      {...props}
+    />
+  )
+}
+
+function AvatarFallback({
+  className,
+  ...props
+}: React.ComponentProps<typeof AvatarPrimitive.Fallback>) {
+  return (
+    <AvatarPrimitive.Fallback
+      data-slot="avatar-fallback"
+      className={cn(
+        "bg-muted flex size-full items-center justify-center rounded-full",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+export { Avatar, AvatarImage, AvatarFallback }