feat: add View Transitions API with persistent backgrounds

- Add fade in/out page transitions using View Transitions API
- Move background/dots to root layout for persistence across routes
- Hide native scrollbar immediately to prevent FOUC
- Set body background in theme script to prevent flash
- Increase inline style threshold for better initial render

web/svelte.config.js

@@ -4,7 +4,7 @@ import { vitePreprocess } from "@sveltejs/vite-plugin-svelte";
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
   preprocess: vitePreprocess(),
-  inlineStyleThreshold: 1000,
+  inlineStyleThreshold: 2000,
   kit: {
     adapter: adapter({
       out: "build",