fix(discord): only send notifications in production

Prevent Discord release notifications from being sent in non-production
environments, avoiding accidental notifications during development and
testing. Added unit tests to verify the behavior.

app/Jobs/DiscordReleaseNotification.php

@@ -31,6 +31,11 @@ class DiscordReleaseNotification implements ShouldQueue
      */
     public function handle(): void
     {
+        // Discord notifications must only ever be sent in production.
+        if (! app()->isProduction()) {
+            return;
+        }
+
         switch ($this->messageType) {
             case 'release':
                 DiscordAlert::message('<@&868457842250764289> (´• ω •`)ﾉ New **4k** Release! Check it out here: https://hstream.moe/hentai/'.$this->slug);