feat(pricing): introduce real-time budget estimator

This commit introduces a real-time budget estimator for event services. A new summary sidebar now displays a live,
itemized breakdown of costs as the user selects options in the order form.

Key changes include:
- A new `OrderSummary` component to display the price breakdown and total.
- Comprehensive pricing logic implemented in the `useEventOrder` composable.
- A responsive two-column layout on the main page to accommodate the summary.
- UI/UX improvements across the form, including clearer labels and subtle transition animations for conditional fields.

app/assets/css/main.css

@@ -1,2 +1,13 @@
 @import "tailwindcss";
 @import "@nuxt/ui";
+
+/* Subtle fade/slide for conditional reveals */
+.fade-enter-active,
+.fade-leave-active {
+  transition: opacity 200ms ease, transform 200ms ease;
+}
+.fade-enter-from,
+.fade-leave-to {
+  opacity: 0;
+  transform: translateY(4px);
+}