add canonical URLs, robots.txt, and sitemap.xml

Canonical: all shop pages now assign og_url (reusing the existing og:url
assign), which the layout renders as <link rel="canonical">. Collection
pages strip the sort param so ?sort=price_asc doesn't create a duplicate
canonical.

robots.txt: dynamic controller disallows /admin/, /api/, /users/,
/webhooks/, /checkout/. Removed robots.txt from static_paths so it
goes through the router instead of Plug.Static.

sitemap.xml: auto-generated from all visible products + categories +
static pages, served as application/xml. 8 tests.

Also updates PROGRESS.md: marks tasks 55, 58, 59, 61, 62 as done.

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

test/berrypod_web/controllers/seo_controller_test.exs

@@ -0,0 +1,68 @@
+defmodule BerrypodWeb.SeoControllerTest do
+  use BerrypodWeb.ConnCase, async: false
+
+  import Berrypod.AccountsFixtures
+  import Berrypod.ProductsFixtures
+
+  setup do
+    user_fixture()
+    {:ok, _} = Berrypod.Settings.set_site_live(true)
+    :ok
+  end
+
+  describe "GET /robots.txt" do
+    test "returns 200 with text/plain content type", %{conn: conn} do
+      conn = get(conn, "/robots.txt")
+      assert response_content_type(conn, :text) =~ "text/plain"
+      assert response(conn, 200)
+    end
+
+    test "allows crawling of shop pages", %{conn: conn} do
+      body = get(conn, "/robots.txt") |> response(200)
+      assert body =~ "User-agent: *"
+      assert body =~ "Allow: /"
+    end
+
+    test "disallows admin and sensitive paths", %{conn: conn} do
+      body = get(conn, "/robots.txt") |> response(200)
+      assert body =~ "Disallow: /admin/"
+      assert body =~ "Disallow: /api/"
+    end
+
+    test "includes sitemap URL", %{conn: conn} do
+      body = get(conn, "/robots.txt") |> response(200)
+      assert body =~ "Sitemap:"
+      assert body =~ "/sitemap.xml"
+    end
+  end
+
+  describe "GET /sitemap.xml" do
+    test "returns 200 with application/xml content type", %{conn: conn} do
+      conn = get(conn, "/sitemap.xml")
+      assert response_content_type(conn, :xml) =~ "application/xml"
+      assert response(conn, 200)
+    end
+
+    test "includes static shop pages", %{conn: conn} do
+      body = get(conn, "/sitemap.xml") |> response(200)
+      assert body =~ "<loc>"
+      assert body =~ "/collections/all"
+      assert body =~ "/about"
+      assert body =~ "/contact"
+    end
+
+    test "includes visible product URLs", %{conn: conn} do
+      product = product_fixture(%{slug: "test-sitemap-tee", visible: true, status: "active"})
+
+      body = get(conn, "/sitemap.xml") |> response(200)
+      assert body =~ "/products/#{product.slug}"
+    end
+
+    test "is valid XML with urlset root element", %{conn: conn} do
+      body = get(conn, "/sitemap.xml") |> response(200)
+      assert body =~ ~s(xmlns="http://www.sitemaps.org/schemas/sitemap/0.9")
+      assert body =~ "<urlset"
+      assert body =~ "</urlset>"
+    end
+  end
+end