Redirect users to default org equipment page on login

Changed signed_in_path to redirect users to their default organization's
equipment page instead of the organization list.

Behavior:
- If user has organizations, redirect to first org's equipment page
- First org is determined by most recently joined (membership.inserted_at)
- If user has no organizations, redirect to /orgs to create one

This provides a better UX by landing users directly at their equipment
list instead of requiring an extra click through the org selector.

lib/towerops_web/user_auth.ex

@@ -217,7 +217,24 @@ defmodule ToweropsWeb.UserAuth do
     end
   end
 
-  defp signed_in_path(_conn), do: ~p"/orgs"
+  defp signed_in_path(conn) do
+    user = conn.assigns[:current_scope] && conn.assigns.current_scope.user
+
+    if user do
+      # Get user's organizations (ordered by most recently joined first)
+      case Towerops.Organizations.list_user_organizations(user.id) do
+        [first_org | _] ->
+          # Redirect to the first organization's equipment page
+          ~p"/orgs/#{first_org.slug}/equipment"
+
+        [] ->
+          # No organizations yet, go to org list
+          ~p"/orgs"
+      end
+    else
+      ~p"/orgs"
+    end
+  end
 
   @doc """
   Plug for routes that require the user to be authenticated.