add no-JS fallback for cart country selector

The delivery country form now has action="/cart/country" with a
noscript submit button. Without JS, changing the country and clicking
Update POSTs to a new CartController.update_country action that saves
the country to session and redirects back to /cart.

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

test/berrypod_web/live/shop/cart_test.exs

@@ -106,6 +106,36 @@ defmodule BerrypodWeb.Shop.CartTest do
     end
   end
 
+  describe "no-JS fallback" do
+    setup [:create_cart_with_product]
+
+    test "country selector form has action for no-JS submission", %{
+      conn: conn,
+      variant: variant
+    } do
+      # Insert a shipping rate so the country selector renders
+      now = DateTime.utc_now() |> DateTime.truncate(:second)
+      pc = Berrypod.ProductsFixtures.provider_connection_fixture()
+
+      Berrypod.Repo.insert_all(Berrypod.Shipping.ShippingRate, [
+        [
+          blueprint_id: 1,
+          print_provider_id: 1,
+          country_code: "GB",
+          first_item_cost: 399,
+          additional_item_cost: 100,
+          provider_connection_id: pc.id,
+          inserted_at: now,
+          updated_at: now
+        ]
+      ])
+
+      {:ok, view, _html} = conn |> conn_with_cart(variant.id) |> live(~p"/cart")
+
+      assert has_element?(view, "form[action='/cart/country'][method='post']")
+    end
+  end
+
   describe "Cart page title" do
     test "page title is Cart", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/cart")