Update the phoenix version and starting migration the project.

assets/js/app.js

@@ -1,7 +1,3 @@
-// We import the CSS which is extracted to its own file by esbuild.
-// Remove this line if you add a your own CSS build pipeline (e.g postcss).
-import "../css/app.css"
-
 // If you want to use Phoenix channels, run `mix help phx.gen.channel`
 // to get started and then uncomment the line below.
 // import "./user_socket.js"
@@ -27,12 +23,15 @@ import {LiveSocket} from "phoenix_live_view"
 import topbar from "../vendor/topbar"
 
 let csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
-let liveSocket = new LiveSocket("/live", Socket, {params: {_csrf_token: csrfToken}})
+let liveSocket = new LiveSocket("/live", Socket, {
+  longPollFallbackMs: 2500,
+  params: {_csrf_token: csrfToken}
+})
 
 // Show progress bar on live navigation and form submits
 topbar.config({barColors: {0: "#29d"}, shadowColor: "rgba(0, 0, 0, .3)"})
-window.addEventListener("phx:page-loading-start", info => topbar.show())
-window.addEventListener("phx:page-loading-stop", info => topbar.hide())
+window.addEventListener("phx:page-loading-start", _info => topbar.show(300))
+window.addEventListener("phx:page-loading-stop", _info => topbar.hide())
 
 // connect if there are any LiveViews on the page
 liveSocket.connect()