fix(porta): Greatly improve HTTP 500 error page (#4382)

<img width="1728" alt="Screenshot 2024-03-28 at 15 00 19"
src="https://github.com/firezone/firezone/assets/1877644/174c54c2-b958-416f-ad50-9c2af4103bfc">

elixir/apps/web/lib/web/controllers/error_html/404.html.heex

@@ -30,7 +30,7 @@
     <div class="flex items-center h-screen p-16 bg-gray-50">
       <div class="container mx-auto flex flex-col items-center">
         <div class="flex flex-col gap-6 max-w-md text-center">
-          <img src="/images/logo.svg" class="mr-5 h-32" alt="Firezone Logo" />
+          <img src={~p"/images/logo.svg"} class="mr-5 h-32" alt="Firezone Logo" />
           <h2 class="font-extrabold text-9xl text-primary-600">
             <span class="sr-only">Error</span>404
           </h2>

elixir/apps/web/lib/web/controllers/error_html/500.html.heex

@@ -30,10 +30,8 @@
     <div class="flex items-center h-screen p-16 bg-gray-50">
       <div class="container mx-auto flex flex-col items-center">
         <div class="flex flex-col gap-6 max-w-md text-center">
-          <img src="/images/logo.svg" class="mr-5 h-32" alt="Firezone Logo" />
-          <h2 class="font-extrabold text-9xl text-primary-600">
-            <span class="sr-only">Error</span>500
-          </h2>
+          <img src={~p"/images/http-500.png"} class="h-auto max-w-full" alt="500 Error" />
+
           <p class="text-2xl md:text-3xl">
             Something went wrong. We've already been notified and will get it fixed as soon as possible.
           </p>