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/collapsible.tsx

@@ -0,0 +1,33 @@
+"use client"
+
+import * as CollapsiblePrimitive from "@radix-ui/react-collapsible"
+
+function Collapsible({
+  ...props
+}: React.ComponentProps<typeof CollapsiblePrimitive.Root>) {
+  return <CollapsiblePrimitive.Root data-slot="collapsible" {...props} />
+}
+
+function CollapsibleTrigger({
+  ...props
+}: React.ComponentProps<typeof CollapsiblePrimitive.CollapsibleTrigger>) {
+  return (
+    <CollapsiblePrimitive.CollapsibleTrigger
+      data-slot="collapsible-trigger"
+      {...props}
+    />
+  )
+}
+
+function CollapsibleContent({
+  ...props
+}: React.ComponentProps<typeof CollapsiblePrimitive.CollapsibleContent>) {
+  return (
+    <CollapsiblePrimitive.CollapsibleContent
+      data-slot="collapsible-content"
+      {...props}
+    />
+  )
+}
+
+export { Collapsible, CollapsibleTrigger, CollapsibleContent }