add URL redirects with ETS-cached plug, broken URL tracking, and admin UI

Redirects context with redirect/broken_url schemas, chain flattening,
ETS cache for fast lookups in the request pipeline. BrokenUrlTracker
plug logs 404s. Auto-redirect on product slug change via upsert_product
hook. Admin redirects page with active/broken tabs, manual create form.
RedirectPrunerWorker cleans up old broken URLs. 1227 tests passing.

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

test/berrypod_web/plugs/broken_url_tracker_test.exs

@@ -0,0 +1,26 @@
+defmodule BerrypodWeb.Plugs.BrokenUrlTrackerTest do
+  use BerrypodWeb.ConnCase, async: true
+
+  alias Berrypod.Redirects
+
+  setup do
+    Redirects.create_table()
+    :ok
+  end
+
+  test "records broken URL on 404", %{conn: conn} do
+    conn = get(conn, "/zz-nonexistent-path")
+
+    assert conn.status in [404, 500]
+
+    [broken_url] = Redirects.list_broken_urls()
+    assert broken_url.path == "/zz-nonexistent-path"
+    assert broken_url.recent_404_count == 1
+  end
+
+  test "skips static asset paths", %{conn: conn} do
+    get(conn, "/assets/missing-file.js")
+
+    assert Redirects.list_broken_urls() == []
+  end
+end

test/berrypod_web/plugs/redirects_test.exs

@@ -0,0 +1,92 @@
+defmodule BerrypodWeb.Plugs.RedirectsTest do
+  use BerrypodWeb.ConnCase, async: true
+
+  alias Berrypod.Redirects
+
+  setup do
+    Redirects.create_table()
+    :ok
+  end
+
+  describe "trailing slash normalisation" do
+    test "strips trailing slash and redirects", %{conn: conn} do
+      conn = get(conn, "/products/foo/")
+
+      assert conn.status == 301
+      assert get_resp_header(conn, "location") == ["/products/foo"]
+    end
+
+    test "preserves query params on trailing slash redirect", %{conn: conn} do
+      conn = get(conn, "/products/foo/?Color=Sand&Size=S")
+
+      assert conn.status == 301
+      assert get_resp_header(conn, "location") == ["/products/foo?Color=Sand&Size=S"]
+    end
+
+    test "does not strip trailing slash from root path", %{conn: conn} do
+      conn = get(conn, "/")
+
+      # Should not redirect — just pass through to the app
+      refute conn.status == 301
+    end
+  end
+
+  describe "case normalisation" do
+    test "lowercases path and redirects", %{conn: conn} do
+      conn = get(conn, "/Products/Foo")
+
+      assert conn.status == 301
+      assert get_resp_header(conn, "location") == ["/products/foo"]
+    end
+
+    test "preserves query param casing", %{conn: conn} do
+      conn = get(conn, "/Products/Foo?Color=Sand")
+
+      assert conn.status == 301
+      assert get_resp_header(conn, "location") == ["/products/foo?Color=Sand"]
+    end
+
+    test "does not redirect already-lowercase paths", %{conn: conn} do
+      # This will get a 404 or 200 from the app, not a 301
+      conn = get(conn, "/products/nonexistent-lowercase-path")
+
+      refute conn.status == 301
+    end
+  end
+
+  describe "custom redirects" do
+    test "redirects matching path with 301", %{conn: conn} do
+      {:ok, _} =
+        Redirects.create_auto(%{
+          from_path: "/products/old-tee",
+          to_path: "/products/new-tee",
+          source: "auto_slug_change"
+        })
+
+      conn = get(conn, "/products/old-tee")
+
+      assert conn.status == 301
+      assert get_resp_header(conn, "location") == ["/products/new-tee"]
+    end
+
+    test "preserves query string on custom redirect", %{conn: conn} do
+      {:ok, _} =
+        Redirects.create_auto(%{
+          from_path: "/products/old-hoodie",
+          to_path: "/products/new-hoodie",
+          source: "auto_slug_change"
+        })
+
+      conn = get(conn, "/products/old-hoodie?Color=Sand&Size=S")
+
+      assert conn.status == 301
+      assert get_resp_header(conn, "location") == ["/products/new-hoodie?Color=Sand&Size=S"]
+    end
+
+    test "passes through when no redirect exists", %{conn: conn} do
+      conn = get(conn, "/products/no-redirect-here")
+
+      refute conn.status == 301
+    end
+  end
+end