add setup foundations: site gate, registration lockdown, coming soon page

- Settings.site_live?/0 and set_site_live/1 for shop visibility control
- Accounts.has_admin?/0 to detect single-tenant admin existence
- Registration lockdown: /users/register redirects when admin exists
- Setup.setup_status/0 aggregates provider, product, and stripe checks
- Coming soon page at /coming-soon with themed styling
- ThemeHook :require_site_live gate on all public shop routes
  - Site live → everyone through
  - Authenticated → admin preview through
  - No admin → fresh install demo through
  - Otherwise → redirect to coming soon
- Go live / take offline toggle on /admin/settings
- 648 tests, 0 failures

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

test/simpleshop_theme_web/live/shop_live/coming_soon_test.exs

@@ -0,0 +1,69 @@
+defmodule SimpleshopThemeWeb.ShopLive.ComingSoonTest do
+  use SimpleshopThemeWeb.ConnCase, async: false
+
+  import Phoenix.LiveViewTest
+  import SimpleshopTheme.AccountsFixtures
+
+  alias SimpleshopTheme.Settings
+
+  describe "coming soon page" do
+    test "renders when site is not live and admin exists", %{conn: conn} do
+      user_fixture()
+
+      {:ok, _view, html} = live(conn, ~p"/coming-soon")
+
+      assert html =~ "Coming soon"
+      assert html =~ "getting things ready"
+    end
+
+    test "displays the shop name", %{conn: conn} do
+      {:ok, _} = Settings.update_theme_settings(%{site_name: "My Test Shop"})
+
+      {:ok, _view, html} = live(conn, ~p"/coming-soon")
+
+      assert html =~ "My Test Shop"
+    end
+  end
+
+  describe "site live gate" do
+    test "redirects unauthenticated visitors to coming soon when not live", %{conn: conn} do
+      # Create admin so the gate activates (fresh installs bypass)
+      user_fixture()
+
+      assert {:error, {:redirect, %{to: "/coming-soon"}}} = live(conn, ~p"/")
+    end
+
+    test "allows authenticated admin through when not live", %{conn: conn} do
+      user = user_fixture()
+      conn = log_in_user(conn, user)
+
+      {:ok, _view, html} = live(conn, ~p"/")
+
+      assert html =~ "Shop the collection"
+    end
+
+    test "allows everyone through when site is live", %{conn: conn} do
+      user_fixture()
+      {:ok, _} = Settings.set_site_live(true)
+
+      {:ok, _view, html} = live(conn, ~p"/")
+
+      assert html =~ "Shop the collection"
+    end
+
+    test "allows everyone through on fresh install (no admin)", %{conn: conn} do
+      # No admin created — fresh install shows the demo shop
+      {:ok, _view, html} = live(conn, ~p"/")
+
+      assert html =~ "Shop the collection"
+    end
+
+    test "gates all public shop routes", %{conn: conn} do
+      user_fixture()
+
+      assert {:error, {:redirect, %{to: "/coming-soon"}}} = live(conn, ~p"/about")
+      assert {:error, {:redirect, %{to: "/coming-soon"}}} = live(conn, ~p"/collections/all")
+      assert {:error, {:redirect, %{to: "/coming-soon"}}} = live(conn, ~p"/cart")
+    end
+  end
+end