switch mp3 to tts, add genserver to app supervisor tree that periodically checks for newly connected devices and plays their associated tts message

lib/here_i_am_web/controllers/page_html/home.html.heex

@@ -3,10 +3,10 @@
 <div class="container mx-auto text-center py-10">
   <article class="prose mx-auto px-4">
     <p>
-      This site allows you to set an MP3 to play when your device connects to the network.
+      This site allows you to set a message to play when your device connects to the network.
     </p>
     <a href="/devices">
-      <button class="btn btn-primary mt-5">Manage Devices</button>
+      <.button class="mt-5">Manage Devices</.button>
     </a>
   </article>
 </div>