Add toast notification system: implement useToast composable and ToastContainer component

app/composables/useToast.ts

@@ -0,0 +1,30 @@
+type Toast = {
+	id: number
+	message: string
+	type?: "success" | "error" | "info"
+}
+
+const toasts = ref<Toast[]>([])
+
+export const useToast = () => {
+	const show = (
+		message: string,
+		type: Toast["type"] = "info",
+		duration = 5 * 1000
+	): number => {
+		const id = toasts.value.length + 1
+		toasts.value.push({ id, message, type })
+
+		setTimeout(() => {
+			remove(id)
+		}, duration)
+
+		return id
+	}
+
+	const remove = (id: number) => {
+		toasts.value = toasts.value.filter((t) => t.id != id)
+	}
+
+	return { toasts, show, remove }
+}