add admin products list and detail pages

Read-mostly admin views for synced products: filterable/sortable list
with inline visibility toggle, and detail page with images grid,
variants table, storefront controls form, and provider edit links.

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

lib/simpleshop_theme/products.ex

@@ -225,6 +225,7 @@ defmodule SimpleshopTheme.Products do
   defp maybe_filter_on_sale(query, _), do: query
 
   defp maybe_filter_in_stock(query, true), do: where(query, [p], p.in_stock == true)
+  defp maybe_filter_in_stock(query, false), do: where(query, [p], p.in_stock == false)
   defp maybe_filter_in_stock(query, _), do: query
 
   defp apply_sort(query, "price_asc"), do: order_by(query, [p], asc: p.cheapest_price)
@@ -264,6 +265,42 @@ defmodule SimpleshopTheme.Products do
     |> Repo.all()
   end
 
+  @doc """
+  Returns products for the admin list page with sorting, stock filtering,
+  and full preloads for display.
+
+  ## Options
+
+    * `:visible` - filter by visibility (boolean)
+    * `:status` - filter by status (string)
+    * `:category` - filter by category (string)
+    * `:provider_connection_id` - filter by provider connection
+    * `:in_stock` - filter by stock status (boolean)
+    * `:sort` - sort order (string)
+
+  """
+  def list_products_admin(opts \\ []) do
+    Product
+    |> apply_product_filters(opts)
+    |> maybe_filter_in_stock(opts[:in_stock])
+    |> apply_sort(opts[:sort])
+    |> preload([:provider_connection, images: :image, variants: []])
+    |> Repo.all()
+  end
+
+  @doc """
+  Returns distinct category names from all products (including hidden/draft).
+  """
+  def list_all_categories do
+    from(p in Product,
+      where: not is_nil(p.category),
+      select: p.category,
+      distinct: true,
+      order_by: p.category
+    )
+    |> Repo.all()
+  end
+
   @doc """
   Gets a single product by ID.
   """
@@ -310,6 +347,22 @@ defmodule SimpleshopTheme.Products do
     |> Repo.update()
   end
 
+  @doc """
+  Updates storefront-only fields (visibility and category).
+  """
+  def update_storefront(%Product{} = product, attrs) do
+    product
+    |> Product.storefront_changeset(attrs)
+    |> Repo.update()
+  end
+
+  @doc """
+  Toggles a product's visibility.
+  """
+  def toggle_visibility(%Product{} = product) do
+    update_storefront(product, %{visible: !product.visible})
+  end
+
   @doc """
   Deletes a product.
   """

lib/simpleshop_theme/products/product.ex

@@ -67,6 +67,14 @@ defmodule SimpleshopTheme.Products.Product do
     |> unique_constraint([:provider_connection_id, :provider_product_id])
   end
 
+  @doc """
+  Changeset for admin storefront controls (visibility and category only).
+  """
+  def storefront_changeset(product, attrs) do
+    product
+    |> cast(attrs, [:visible, :category])
+  end
+
   @doc """
   Changeset for recomputing denormalized fields from variants.
   """