switch mockup generator to UK print providers and add --replace flag

- Prefer Print Clever (72) for canvas, Monster Digital (29) for
  apparel and mugs where available, fall back to default providers
- Rename Art Print products to Canvas (new Satin Canvas blueprint)
- Add Canvas Prints category in Printify tag extraction
- Add --replace/-r flag to purge existing Printify products before
  generating (with interactive confirmation)
- Add purge_all_products/1 to generator module
- Remove old art print mockups, add new canvas + extra provider mockups

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

lib/mix/tasks/generate_mockups.ex

@@ -16,6 +16,9 @@ defmodule Mix.Tasks.GenerateMockups do
       # Generate mockups (keeps products in Printify)
       mix generate_mockups
 
+      # Delete existing products first, then generate fresh ones
+      mix generate_mockups --replace
+
       # Generate mockups and delete products afterwards
       mix generate_mockups --cleanup
 
@@ -45,12 +48,14 @@ defmodule Mix.Tasks.GenerateMockups do
       OptionParser.parse(args,
         switches: [
           cleanup: :boolean,
+          replace: :boolean,
           search: :string,
           list_blueprints: :boolean,
           help: :boolean
         ],
         aliases: [
           c: :cleanup,
+          r: :replace,
           s: :search,
           l: :list_blueprints,
           h: :help
@@ -84,6 +89,7 @@ defmodule Mix.Tasks.GenerateMockups do
       mix generate_mockups [options]
 
     Options:
+      --replace, -r       Delete ALL existing products from Printify before generating (with confirmation)
       --cleanup, -c       Delete created products from Printify after downloading mockups
       --search, -s TERM   Search for blueprints by name
       --list-blueprints   List all available blueprint IDs and names
@@ -149,12 +155,14 @@ defmodule Mix.Tasks.GenerateMockups do
 
   defp generate_mockups(opts) do
     cleanup = Keyword.get(opts, :cleanup, false)
+    replace = Keyword.get(opts, :replace, false)
 
     Mix.shell().info("""
 
     ╔═══════════════════════════════════════════╗
     ║     Printify Mockup Generator             ║
     ╠═══════════════════════════════════════════╣
+    ║  Replace mode: #{if replace, do: "ON ", else: "OFF"}                        ║
     ║  Cleanup mode: #{if cleanup, do: "ON ", else: "OFF"}                        ║
     ╚═══════════════════════════════════════════╝
 
@@ -177,6 +185,8 @@ defmodule Mix.Tasks.GenerateMockups do
         """)
 
       _token ->
+        if replace, do: purge_existing_products()
+
         results = MockupGenerator.generate_all(cleanup: cleanup)
 
         # Summary
@@ -200,4 +210,27 @@ defmodule Mix.Tasks.GenerateMockups do
         end
     end
   end
+
+  defp purge_existing_products do
+    alias SimpleshopTheme.Clients.Printify, as: Client
+
+    Mix.shell().info("Fetching existing products...")
+
+    {:ok, shop_id} = Client.get_shop_id()
+    {:ok, %{"data" => products}} = Client.list_products(shop_id)
+    count = length(products)
+
+    if count == 0 do
+      Mix.shell().info("No existing products to delete.\n")
+    else
+      Mix.shell().info("Found #{count} existing products in Printify.")
+
+      if Mix.shell().yes?("Delete all #{count} products before generating new ones?") do
+        deleted = MockupGenerator.purge_all_products(shop_id)
+        Mix.shell().info("Deleted #{deleted} products.\n")
+      else
+        Mix.shell().info("Skipping purge.\n")
+      end
+    end
+  end
 end