fix: handle Printful v2 API list response format

v2 returns {data: [...]} (array) not {data: {...}} (object).
Also fixes mockup task polling to use ?id= query param and
extracts mockup_url from nested catalog_variant_mockups structure.

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

backend/app/api/designs.py

@@ -166,16 +166,13 @@ async def _get_printful_mockup(slug: str, product) -> bytes | None:
         if not mockups:
             return None
 
-        # v2 response: catalog_variant_mockups → each has mockup_url or
-        # placements[].mockup_url. Also check legacy "url" field.
+        # v2 response: catalog_variant_mockups[] → .mockups[] → .mockup_url
         mockup_url = None
-        for m in mockups:
-            mockup_url = m.get("mockup_url") or m.get("url")
-            if not mockup_url and "placements" in m:
-                for p in m["placements"]:
-                    mockup_url = p.get("mockup_url") or p.get("url")
-                    if mockup_url:
-                        break
+        for variant_mockup in mockups:
+            for mockup in variant_mockup.get("mockups", []):
+                mockup_url = mockup.get("mockup_url") or mockup.get("url")
+                if mockup_url:
+                    break
             if mockup_url:
                 break
 

backend/app/pod/printful_client.py

@@ -138,7 +138,9 @@ class PrintfulClient:
                 json=payload,
             )
             resp.raise_for_status()
-            data = resp.json().get("data", {})
+            # v2 returns {"data": [{ ... }]} — data is a list
+            raw_data = resp.json().get("data", [])
+            data = raw_data[0] if isinstance(raw_data, list) and raw_data else raw_data
             task_id = data.get("id") or data.get("task_key") or data.get("task_id")
             logger.info(f"Printful mockup task created: {task_id}")
             return str(task_id)
@@ -151,11 +153,16 @@ class PrintfulClient:
         """
         async with httpx.AsyncClient(timeout=15.0) as client:
             resp = await client.get(
-                f"{BASE_URL}/mockup-tasks/{task_id}",
+                f"{BASE_URL}/mockup-tasks",
                 headers=self._headers,
+                params={"id": task_id},
             )
             resp.raise_for_status()
-            return resp.json().get("data", {})
+            # v2 returns {"data": [{ ... }]} — data is a list
+            raw_data = resp.json().get("data", [])
+            if isinstance(raw_data, list) and raw_data:
+                return raw_data[0]
+            return raw_data if isinstance(raw_data, dict) else {}
 
     async def generate_mockup_and_wait(
         self,