feat(analytics): integrate Umami analytics

This commit introduces Umami analytics for website usage tracking.

- Adds a new `analytics.js` file to the `public` directory to load the Umami tracking script.
- Updates `nuxt.config.ts` to inject this script into the document head and configure the page title.

Additionally, this commit fixes the referrer note display by removing a hardcoded prefix.

app/composables/eventOrder.ts

@@ -21,9 +21,9 @@ export const _useEventOrder = () => {
 
   const refererNote = computed(() => {
     const key = refererKey.value as keyof typeof REFERRER_MAP;
-    return key in REFERRER_MAP ? `推薦單位：${REFERRER_MAP[key]}` : "";
+    return key in REFERRER_MAP ? REFERRER_MAP[key] : "";
   });
-  
+
   function formatLocalDate(date: Date): string {
     const y = date.getFullYear();
     const m = String(date.getMonth() + 1).padStart(2, "0");