feat(ui) : error toasts persist until dismissed, add progress bar on auto-dismiss toasts

frontend/app/components/ToastContainer.vue

@@ -13,7 +13,7 @@
         ]"
       >
         <div
-          class="alert toast-card shadow-md px-3 py-2 text-sm"
+          class="alert toast-card relative shadow-md px-3 py-2 text-sm overflow-hidden"
           :class="getToastClasses(toast.type)"
         >
           <div class="flex items-center gap-2">
@@ -54,6 +54,13 @@
               <IconLucideX class="w-3 h-3" aria-hidden="true" />
             </button>
           </div>
+
+          <!-- Progress bar for auto-dismiss toasts -->
+          <div
+            v-if="toast.duration > 0"
+            class="absolute bottom-0 left-0 h-0.5 bg-current opacity-30 rounded-full"
+            :style="{ animation: `toast-progress ${toast.duration}ms linear forwards` }"
+          />
         </div>
       </div>
     </TransitionGroup>
@@ -111,4 +118,9 @@ const getToastClasses = (type) => {
   pointer-events: auto;
   border-radius: 0.75rem;
 }
+
+@keyframes toast-progress {
+  from { width: 100%; }
+  to { width: 0%; }
+}
 </style>