gate magic link login on verified email delivery

The login page now only shows the magic link form when a test email has
been sent successfully, not just when an adapter is configured. Saving
email settings or disconnecting clears the flag so the admin must
re-verify after config changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/live/admin/email_settings.ex

@@ -94,6 +94,8 @@ defmodule BerrypodWeb.Admin.EmailSettings do
         Settings.delete_setting(key)
       end
 
+      Mailer.clear_email_verified()
+
       # Reset to Local adapter
       Application.put_env(:berrypod, Mailer, adapter: Swoosh.Adapters.Local)
 
@@ -113,6 +115,8 @@ defmodule BerrypodWeb.Admin.EmailSettings do
 
     case Mailer.send_test_email(user.email, socket.assigns.from_address) do
       {:ok, _} ->
+        Mailer.mark_email_verified()
+
         {:noreply,
          socket
          |> assign(:sending_test, false)
@@ -174,6 +178,9 @@ defmodule BerrypodWeb.Admin.EmailSettings do
         Settings.put_setting("email_from_address", from_address)
       end
 
+      # Config changed — require re-verification
+      Mailer.clear_email_verified()
+
       # Apply config immediately
       Mailer.load_config()