make admin provider UI support both Printify and Printful

- Provider form accepts ?type= query param (printify/printful)
- Conditional setup instructions per provider (API key steps, login URLs)
- Dynamic labels, titles, and config handling (shop_id vs store_id)
- Provider index shows dropdown with both provider options
- Settings page renamed from @printify to @provider (generic)
- Fix Printful shipping rates: add default state codes for US/CA/AU

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

test/simpleshop_theme_web/live/admin/providers_test.exs

@@ -33,13 +33,14 @@ defmodule SimpleshopThemeWeb.Admin.ProvidersTest do
     test "shows empty state when no connections exist", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/admin/providers")
 
-      assert html =~ "Connect your Printify account"
+      assert html =~ "Connect a print-on-demand provider"
     end
 
-    test "shows connect button", %{conn: conn} do
+    test "shows connect buttons for both providers", %{conn: conn} do
       {:ok, view, _html} = live(conn, ~p"/admin/providers")
 
-      assert has_element?(view, ~s(a[href="/admin/providers/new"]))
+      assert has_element?(view, ~s(a[href="/admin/providers/new?type=printify"]))
+      assert has_element?(view, ~s(a[href="/admin/providers/new?type=printful"]))
     end
   end
 
@@ -138,12 +139,26 @@ defmodule SimpleshopThemeWeb.Admin.ProvidersTest do
       %{conn: log_in_user(conn, user)}
     end
 
-    test "renders new form", %{conn: conn} do
+    test "renders new Printify form", %{conn: conn} do
+      {:ok, _view, html} = live(conn, ~p"/admin/providers/new?type=printify")
+
+      assert html =~ "Connect to Printify"
+      assert html =~ "Printify API key"
+      assert html =~ "Log in to Printify"
+    end
+
+    test "renders new Printful form", %{conn: conn} do
+      {:ok, _view, html} = live(conn, ~p"/admin/providers/new?type=printful")
+
+      assert html =~ "Connect to Printful"
+      assert html =~ "Printful API key"
+      assert html =~ "Log in to Printful"
+    end
+
+    test "defaults to Printify when no type param", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/admin/providers/new")
 
       assert html =~ "Connect to Printify"
-      assert html =~ "connection key"
-      assert html =~ "Log in to Printify"
     end
 
     test "test connection shows error when no api key", %{conn: conn} do
@@ -151,7 +166,7 @@ defmodule SimpleshopThemeWeb.Admin.ProvidersTest do
 
       html = render_click(view, "test_connection")
 
-      assert html =~ "Please enter your connection key"
+      assert html =~ "Please enter your API key"
     end
 
     test "saves new connection", %{conn: conn} do

test/simpleshop_theme_web/live/admin/settings_test.exs

@@ -151,7 +151,7 @@ defmodule SimpleshopThemeWeb.Admin.SettingsTest do
 
       assert html =~ "Products"
       assert html =~ "Not connected"
-      assert has_element?(view, ~s(a[href="/admin/providers/new"]), "Connect to Printify")
+      assert has_element?(view, ~s(a[href="/admin/providers"]), "Connect a provider")
     end
 
     test "shows connection info when provider connected", %{conn: conn} do