add FTS5 full-text product search

Adds SQLite FTS5 search index with BM25 ranking across product title,
category, variant attributes, and description. Search modal now has
live results with thumbnails, prices, and click-to-navigate. Index
rebuilds automatically after each provider sync.

Also fixes Access syntax on Product/ProductImage structs (Map.get
instead of bracket notation) which was causing crashes when real
products were loaded from the database.

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

test/simpleshop_theme/search_test.exs

@@ -0,0 +1,199 @@
+defmodule SimpleshopTheme.SearchTest do
+  use SimpleshopTheme.DataCase, async: false
+
+  alias SimpleshopTheme.Search
+
+  import SimpleshopTheme.ProductsFixtures
+
+  setup do
+    conn = provider_connection_fixture()
+
+    mountain =
+      product_fixture(%{
+        provider_connection: conn,
+        title: "Mountain Sunrise Art Print",
+        description: "<p>A beautiful <strong>mountain</strong> landscape at dawn.</p>",
+        category: "Art Prints"
+      })
+
+    product_variant_fixture(%{
+      product: mountain,
+      title: "Small / Navy",
+      options: %{"Size" => "Small", "Color" => "Navy"},
+      price: 1999
+    })
+
+    ocean =
+      product_fixture(%{
+        provider_connection: conn,
+        title: "Ocean Waves Notebook",
+        description: "A spiral-bound notebook with ocean wave cover art.",
+        category: "Stationery"
+      })
+
+    product_variant_fixture(%{
+      product: ocean,
+      title: "A5",
+      options: %{"Size" => "A5"},
+      price: 1299
+    })
+
+    forest =
+      product_fixture(%{
+        provider_connection: conn,
+        title: "Forest Silhouette T-Shirt",
+        description: "Cotton t-shirt with forest silhouette print.",
+        category: "Apparel"
+      })
+
+    product_variant_fixture(%{
+      product: forest,
+      title: "Large / Black",
+      options: %{"Size" => "Large", "Color" => "Black"},
+      price: 2999
+    })
+
+    product_variant_fixture(%{
+      product: forest,
+      title: "Medium / Navy Blue",
+      options: %{"Size" => "Medium", "Color" => "Navy Blue"},
+      price: 2999
+    })
+
+    # Hidden product — should not appear in search
+    _hidden =
+      product_fixture(%{
+        provider_connection: conn,
+        title: "Hidden Mountain Poster",
+        description: "This should not be searchable.",
+        category: "Art Prints",
+        visible: false
+      })
+
+    Search.rebuild_index()
+
+    %{mountain: mountain, ocean: ocean, forest: forest}
+  end
+
+  describe "search/1" do
+    test "finds products by title", %{mountain: mountain} do
+      results = Search.search("mountain")
+      assert length(results) >= 1
+      assert Enum.any?(results, &(&1.id == mountain.id))
+    end
+
+    test "finds products by category", %{mountain: mountain, ocean: ocean} do
+      results = Search.search("art prints")
+      assert Enum.any?(results, &(&1.id == mountain.id))
+      refute Enum.any?(results, &(&1.id == ocean.id))
+    end
+
+    test "finds products by variant attributes", %{forest: forest} do
+      results = Search.search("navy")
+      assert Enum.any?(results, &(&1.id == forest.id))
+    end
+
+    test "finds products by description", %{mountain: mountain} do
+      results = Search.search("landscape")
+      assert Enum.any?(results, &(&1.id == mountain.id))
+    end
+
+    test "prefix matching on last token", %{mountain: mountain} do
+      results = Search.search("mou")
+      assert Enum.any?(results, &(&1.id == mountain.id))
+    end
+
+    test "multi-word query matches all tokens", %{mountain: mountain} do
+      results = Search.search("mountain sunrise")
+      assert Enum.any?(results, &(&1.id == mountain.id))
+    end
+
+    test "returns empty list for blank query" do
+      assert Search.search("") == []
+      assert Search.search("  ") == []
+    end
+
+    test "returns empty list for single character" do
+      assert Search.search("a") == []
+    end
+
+    test "returns empty list for nil" do
+      assert Search.search(nil) == []
+    end
+
+    test "returns empty list for no matches" do
+      assert Search.search("xyznonexistent") == []
+    end
+
+    test "special characters don't crash" do
+      assert Search.search("mountain's") == Search.search("mountains")
+      assert Search.search("test & foo") == []
+      assert Search.search("(brackets)") == []
+    end
+
+    test "hidden products are excluded" do
+      results = Search.search("hidden")
+      assert results == []
+    end
+
+    test "strips HTML from descriptions", %{mountain: mountain} do
+      results = Search.search("landscape dawn")
+      assert Enum.any?(results, &(&1.id == mountain.id))
+    end
+
+    test "results include listing preloads", %{mountain: mountain} do
+      [result | _] = Search.search("mountain sunrise")
+      assert result.id == mountain.id
+      assert Ecto.assoc_loaded?(result.images)
+    end
+
+    test "title matches rank higher than description matches" do
+      results = Search.search("mountain")
+      # Mountain Sunrise Art Print (title match) should rank above
+      # Forest T-Shirt if it happened to mention "mountain" in description
+      first = List.first(results)
+      assert first.title =~ "Mountain"
+    end
+  end
+
+  describe "rebuild_index/0" do
+    test "rebuilds from scratch" do
+      # Verify search works before rebuild
+      assert length(Search.search("mountain")) >= 1
+
+      # Rebuild and verify still works
+      Search.rebuild_index()
+      assert length(Search.search("mountain")) >= 1
+    end
+  end
+
+  describe "index_product/1" do
+    test "indexes a single product", %{ocean: ocean} do
+      # Clear and rebuild without ocean
+      SimpleshopTheme.Repo.query!("DELETE FROM products_search_map")
+      SimpleshopTheme.Repo.query!("DELETE FROM products_search")
+
+      assert Search.search("ocean") == []
+
+      # Index just ocean
+      ocean = SimpleshopTheme.Repo.preload(ocean, [:variants])
+      Search.index_product(ocean)
+
+      results = Search.search("ocean")
+      assert length(results) == 1
+      assert hd(results).id == ocean.id
+    end
+
+    test "reindexing updates existing entry", %{mountain: mountain} do
+      # Change title and reindex
+      mountain =
+        mountain
+        |> Ecto.Changeset.change(title: "Alpine Sunrise Art Print")
+        |> SimpleshopTheme.Repo.update!()
+
+      Search.index_product(mountain)
+
+      assert Search.search("alpine") != []
+    end
+  end
+end