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.

nuxt.config.ts

@@ -4,4 +4,16 @@ export default defineNuxtConfig({
   devtools: { enabled: true },
   modules: ["@nuxt/ui"],
   css: ["~/assets/css/main.css"],
+  app: {
+    head: {
+      titleTemplate: "%s | Tootaio Studio",
+      title: "报价单",
+      script: [
+        {
+          src: "/analytics.js",
+          tagPosition: "head",
+        },
+      ],
+    },
+  },
 });