feat: enhance user interface with improved styling and responsiveness

- Updated UserAvatar component to accept additional className for better customization.
- Refined ProfilePage layout with responsive avatar styling.
- Enhanced Header component with improved background and text styles.
- Improved PopularTags and TopFriends components with better spacing and text shadows.
- Updated ThoughtCard and ThoughtThread components for better visual hierarchy and responsiveness.
- Enhanced UI components (Button, Badge, Card, DropdownMenu, Input, Popover, Separator, Skeleton, Textarea) with new styles and effects.
- Added a new background image for visual enhancement.

thoughts-frontend/components/thought-thread.tsx

@@ -34,7 +34,7 @@ export function ThoughtThread({
       />
 
       {directReplies.length > 0 && (
-        <div className="pl-6 border-l-2 border-dashed ml-6 flex flex-col gap-4 pt-4">
+        <div className="pl-6 border-l-2 border-primary/30 border-dashed ml-6 flex flex-col gap-4 pt-4">
           {directReplies.map((reply) => (
             <ThoughtThread // RECURSIVE CALL
               key={reply.id}