refactor: modularize chat backend, update docs for .m4s segments

infrastructure/cloudflare/worker.js

@@ -6,8 +6,8 @@ addEventListener("fetch", (event) => {
 async function handleRequest(request) {
   const url = new URL(request.url);
 
-  // Add immutable cache headers for .ts segments
-  if (url.pathname.endsWith(".ts")) {
+  // Add immutable cache headers for .m4s segments
+  if (url.pathname.endsWith(".m4s")) {
     const response = await fetch(request);
     const headers = new Headers(response.headers);
     headers.set("Cache-Control", "public, max-age=31536000, immutable");