feat: add discovery page for browsing content.

Frontend-Learner/pages/browse/discovery.vue

@@ -189,7 +189,7 @@ const { currentUser } = useAuth();
       <div class="flex flex-col md:flex-row md:items-center justify-between gap-4 mb-8">
         <!-- Title -->
         <h2 class="text-2xl font-bold text-slate-900 dark:text-white">
-          รายการคอร์สทั้งหมด
+          {{ $t('discovery.title') }}
         </h2>
 
         <!-- Right Side: Search & Sort -->