add page builder polish: utility blocks, templates, duplicate

New block types: spacer, divider, button/CTA, video embed (YouTube,
Vimeo with privacy-enhanced embeds, fallback for unknown URLs).

Page templates (blank, content, landing) shown when creating custom
pages. Duplicate page action on admin index with slug deduplication.

Fix block picker on shop edit sidebar being cut off on mobile by
accounting for bottom nav and making the grid scrollable.

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

test/berrypod/pages_test.exs

@@ -564,4 +564,73 @@ defmodule Berrypod.PagesTest do
       refute Page.reserved_path?("faq")
     end
   end
+
+  describe "templates" do
+    test "templates/0 returns available templates" do
+      templates = Defaults.templates()
+
+      assert length(templates) == 3
+      keys = Enum.map(templates, & &1.key)
+      assert "blank" in keys
+      assert "content" in keys
+      assert "landing" in keys
+    end
+
+    test "template_blocks/1 returns blocks for content template" do
+      blocks = Defaults.template_blocks("content")
+
+      types = Enum.map(blocks, & &1["type"])
+      assert types == ["hero", "content_body"]
+    end
+
+    test "template_blocks/1 returns blocks for landing template" do
+      blocks = Defaults.template_blocks("landing")
+
+      types = Enum.map(blocks, & &1["type"])
+      assert "hero" in types
+      assert "featured_products" in types
+      assert "button" in types
+    end
+
+    test "template_blocks/1 returns empty list for blank" do
+      assert Defaults.template_blocks("blank") == []
+    end
+
+    test "template blocks have unique IDs" do
+      for tmpl <- Defaults.templates() do
+        blocks = Defaults.template_blocks(tmpl.key)
+        ids = Enum.map(blocks, & &1["id"])
+        assert ids == Enum.uniq(ids), "duplicate IDs in #{tmpl.key} template"
+      end
+    end
+  end
+
+  describe "duplicate_custom_page/1" do
+    test "creates a draft copy with -copy slug" do
+      {:ok, original} =
+        Pages.create_custom_page(%{
+          "slug" => "test-original",
+          "title" => "Test Page",
+          "blocks" => [%{"id" => "blk_1", "type" => "hero", "settings" => %{"title" => "Hello"}}]
+        })
+
+      {:ok, copy} = Pages.duplicate_custom_page(original)
+
+      assert copy.slug == "test-original-copy"
+      assert copy.title == "Test Page (copy)"
+      assert copy.published == false
+      assert length(copy.blocks) == 1
+      assert hd(copy.blocks)["type"] == "hero"
+    end
+
+    test "deduplicates slug when copy already exists" do
+      {:ok, original} =
+        Pages.create_custom_page(%{"slug" => "dup-test", "title" => "Dup Test"})
+
+      {:ok, _first_copy} = Pages.duplicate_custom_page(original)
+      {:ok, second_copy} = Pages.duplicate_custom_page(original)
+
+      assert second_copy.slug == "dup-test-copy-2"
+    end
+  end
 end