Update validation message for URL configuration

The commit updates the validation error message in the chat web app configuration. The new message indicates a scenario where a user has provided the URL using http instead of https during a production build, increasing clarity by hinting at possible misconfigurations due to incorrect protocol use.

apps/web/config/app.config.ts

@@ -25,7 +25,7 @@ const AppConfigSchema = z
         required_error: `Please provide the variable NEXT_PUBLIC_SITE_URL`,
       })
       .url({
-        message: `Please provide a valid URL. Example: 'https://example.com'`,
+        message: `You are deploying a production build but have entered a NEXT_PUBLIC_SITE_URL variable using http instead of https. It is very likely that you have set the incorrect URL. The build will now fail to prevent you from from deploying a faulty configuration. Please provide the variable NEXT_PUBLIC_SITE_URL with a valid URL, such as: 'https://example.com'`,
       }),
     locale: z
       .string({