feat: add Printify webhook endpoint for real-time product updates

- Add /webhooks/printify endpoint with HMAC-SHA256 signature verification
- Add Webhooks context to handle product:updated, product:deleted events
- Add ProductDeleteWorker for async product deletion
- Add webhook API methods to Printify client (create, list, delete)
- Add register_webhooks/2 to Printify provider
- Add mix register_webhooks task for one-time webhook registration
- Cache raw request body in endpoint for signature verification

Usage:
1. Generate webhook secret: openssl rand -hex 20
2. Add to provider connection config as "webhook_secret"
3. Register with Printify: mix register_webhooks https://yourshop.com/webhooks/printify

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/simpleshop_theme/clients/printify.ex

@@ -183,6 +183,41 @@ defmodule SimpleshopTheme.Clients.Printify do
     get("/shops/#{shop_id}/orders/#{order_id}.json")
   end
 
+  # =============================================================================
+  # Webhooks
+  # =============================================================================
+
+  @doc """
+  Register a webhook with Printify.
+
+  ## Event types
+  - "product:publish:started"
+  - "product:updated"
+  - "product:deleted"
+  - "shop:disconnected"
+  """
+  def create_webhook(shop_id, url, topic, secret) do
+    post("/shops/#{shop_id}/webhooks.json", %{
+      topic: topic,
+      url: url,
+      secret: secret
+    })
+  end
+
+  @doc """
+  List registered webhooks for a shop.
+  """
+  def list_webhooks(shop_id) do
+    get("/shops/#{shop_id}/webhooks.json")
+  end
+
+  @doc """
+  Delete a webhook.
+  """
+  def delete_webhook(shop_id, webhook_id) do
+    delete("/shops/#{shop_id}/webhooks/#{webhook_id}.json")
+  end
+
   @doc """
   Download a file from a URL to a local path.
   """

lib/simpleshop_theme/providers/printify.ex

@@ -114,6 +114,66 @@ defmodule SimpleshopTheme.Providers.Printify do
     end
   end
 
+  # =============================================================================
+  # Webhook Registration
+  # =============================================================================
+
+  @webhook_events ["product:updated", "product:deleted", "product:publish:started"]
+
+  @doc """
+  Registers webhooks for product events with Printify.
+
+  Returns {:ok, results} or {:error, reason}.
+  """
+  def register_webhooks(%ProviderConnection{config: config} = conn, webhook_url) do
+    shop_id = config["shop_id"]
+    secret = config["webhook_secret"]
+
+    cond do
+      is_nil(shop_id) ->
+        {:error, :no_shop_id}
+
+      is_nil(secret) or secret == "" ->
+        {:error, :no_webhook_secret}
+
+      true ->
+        with api_key when is_binary(api_key) <- ProviderConnection.get_api_key(conn),
+             :ok <- set_api_key(api_key) do
+          results =
+            Enum.map(@webhook_events, fn event ->
+              case Client.create_webhook(shop_id, webhook_url, event, secret) do
+                {:ok, response} -> {:ok, event, response}
+                {:error, reason} -> {:error, event, reason}
+              end
+            end)
+
+          {:ok, results}
+        else
+          nil -> {:error, :no_api_key}
+        end
+    end
+  end
+
+  @doc """
+  Lists registered webhooks for the shop.
+  """
+  def list_webhooks(%ProviderConnection{config: config} = conn) do
+    shop_id = config["shop_id"]
+
+    if is_nil(shop_id) do
+      {:error, :no_shop_id}
+    else
+      with api_key when is_binary(api_key) <- ProviderConnection.get_api_key(conn),
+           :ok <- set_api_key(api_key),
+           {:ok, webhooks} <- Client.list_webhooks(shop_id) do
+        {:ok, webhooks}
+      else
+        nil -> {:error, :no_api_key}
+        {:error, _} = error -> error
+      end
+    end
+  end
+
   # =============================================================================
   # Data Normalization
   # =============================================================================

lib/simpleshop_theme/webhooks.ex

@@ -0,0 +1,45 @@
+defmodule SimpleshopTheme.Webhooks do
+  @moduledoc """
+  Handles incoming webhook events from POD providers.
+  """
+
+  alias SimpleshopTheme.Products
+  alias SimpleshopTheme.Sync.ProductSyncWorker
+  alias SimpleshopTheme.Webhooks.ProductDeleteWorker
+
+  require Logger
+
+  @doc """
+  Handles a Printify webhook event.
+
+  Returns :ok or {:ok, job} on success, {:error, reason} on failure.
+  """
+  def handle_printify_event("product:updated", %{"id" => _product_id}) do
+    enqueue_product_sync()
+  end
+
+  def handle_printify_event("product:publish:started", %{"id" => _product_id}) do
+    enqueue_product_sync()
+  end
+
+  def handle_printify_event("product:deleted", %{"id" => product_id}) do
+    ProductDeleteWorker.enqueue(product_id)
+  end
+
+  def handle_printify_event("shop:disconnected", _resource) do
+    Logger.warning("Printify shop disconnected - manual intervention needed")
+    :ok
+  end
+
+  def handle_printify_event(event_type, _resource) do
+    Logger.info("Ignoring unhandled Printify event: #{event_type}")
+    :ok
+  end
+
+  defp enqueue_product_sync do
+    case Products.get_provider_connection_by_type("printify") do
+      nil -> {:error, :no_connection}
+      conn -> ProductSyncWorker.enqueue(conn.id)
+    end
+  end
+end

lib/simpleshop_theme/webhooks/product_delete_worker.ex

@@ -0,0 +1,41 @@
+defmodule SimpleshopTheme.Webhooks.ProductDeleteWorker do
+  @moduledoc """
+  Oban worker for deleting products removed from POD providers.
+  """
+
+  use Oban.Worker, queue: :sync, max_attempts: 3
+
+  alias SimpleshopTheme.Products
+
+  require Logger
+
+  @impl Oban.Worker
+  def perform(%Oban.Job{args: %{"provider_product_id" => provider_product_id}}) do
+    case Products.get_provider_connection_by_type("printify") do
+      nil ->
+        Logger.warning("No Printify connection found for product deletion")
+        {:cancel, :no_connection}
+
+      conn ->
+        case Products.get_product_by_provider(conn.id, provider_product_id) do
+          nil ->
+            Logger.info("Product #{provider_product_id} already deleted or not found")
+            :ok
+
+          product ->
+            Logger.info("Deleting product #{product.id} (provider: #{provider_product_id})")
+
+            case Products.delete_product(product) do
+              {:ok, _} -> :ok
+              {:error, reason} -> {:error, reason}
+            end
+        end
+    end
+  end
+
+  def enqueue(provider_product_id) do
+    %{provider_product_id: to_string(provider_product_id)}
+    |> new()
+    |> Oban.insert()
+  end
+end