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/header.tsx

@@ -5,22 +5,22 @@ import Link from "next/link";
 import { Button } from "./ui/button";
 import { UserNav } from "./user-nav";
 import { MainNav } from "./main-nav";
-import { ThemeToggle } from "./theme-toggle";
 
 export function Header() {
   const { token } = useAuth();
 
   return (
-    <header className="sticky top-0 z-50 w-full border-b bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/60">
-      <div className="w-full flex h-14 items-center px-2">
+    <header className="sticky top-0 z-50 flex justify-center w-full border-b border-primary/20 bg-background/80 backdrop-blur-xl supports-[backdrop-filter]:bg-background/60 glossy-effect bottom">
+      <div className="container flex h-14 items-center px-2">
         <div className="flex gap-2">
           <Link href="/" className="flex items-center gap-1">
-            <span className="hidden font-bold sm:inline-block">Thoughts</span>
+            <span className="hidden font-bold text-primary sm:inline-block">
+              Thoughts
+            </span>
           </Link>
           <MainNav />
         </div>
         <div className="flex flex-1 items-center justify-end space-x-2">
-          <ThemeToggle />
           {token ? (
             <UserNav />
           ) : (