Refactor UI components for improved styling and user experience

- Updated UserMenu.vue to enhance button and avatar styles for a more modern look.
- Adjusted alert component styles in index.ts for consistent rounded corners.
- Simplified loading state markup in order confirmation page for cleaner code.
- Enhanced button and link text for better clarity and user navigation.

These changes aim to improve the overall aesthetic and usability of the application, ensuring a more cohesive user experience.

app/components/UserMenu.vue

@@ -44,24 +44,24 @@ async function handleLogout() {
 <template>
   <!-- Not logged in: Show login prompt -->
   <NuxtLink v-if="!loggedIn" to="/auth"
-    class="flex items-center gap-2 px-4 py-2 rounded-2xl border-2 border-dashed border-muted-foreground/30 hover:border-experimenta-accent hover:bg-experimenta-accent/10 transition-all"
+    class="flex items-center gap-2 px-4 py-2 rounded-[35px] border-2 border-dashed border-muted-foreground/30 hover:border-experimenta-accent hover:bg-experimenta-accent/10 transition-all"
     aria-label="Anmelden oder Registrieren">
     <Avatar class="h-10 w-10 border-2 border-muted-foreground/30 rounded-2xl">
       <AvatarFallback class="bg-muted text-muted-foreground rounded-2xl">
         <User class="h-5 w-5" />
       </AvatarFallback>
     </Avatar>
-    <span class="text-sm font-medium hidden sm:inline">Anmelden</span>
+    <span class="font-medium hidden sm:inline">Anmelden</span>
   </NuxtLink>
 
   <!-- Logged in: Show user menu -->
   <DropdownMenu v-else>
     <DropdownMenuTrigger as-child>
       <button
-        class="flex items-center gap-3 rounded-2xl px-2 py-1.5 focus:outline-none focus:ring-2 focus:ring-experimenta-accent focus:ring-offset-2 transition-all hover:bg-white/10"
+        class="flex items-center gap-3 rounded-[35px] px-2 py-1.5 focus:outline-none focus:ring-2 focus:ring-experimenta-accent focus:ring-offset-2 transition-all hover:bg-white/10"
         aria-label="Benutzermenü öffnen">
         <!-- Greeting text (Desktop only) -->
-        <span class="hidden md:inline font-medium text-white">
+        <span class="hidden md:inline font-medium text-white pl-2">
           Hallo, {{ user?.firstName }}
         </span>