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

priv/repo/migrations/20240713185614_create_devices.exs

@@ -4,7 +4,7 @@ defmodule HereIAm.Repo.Migrations.CreateDevices do
   def change do
     create table(:devices) do
       add :ip_address, :string
-      add :audio, :string
+      add :tts, :string
 
       timestamps(type: :utc_datetime)
     end