Gallery test queries by portal id (membership is portal-keyed)

Follow-through from the portal-keyed gallery fix: the rewritten
test_document_list still queried by a free-form tag.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: nofurtherinformation

backend/tests/test_main.py

@@ -1412,7 +1412,9 @@ def test_document_list(
         },
     )
     assert response.status_code == 201, response.json()
-    response = client.get("/api/documents/list?tags=test")
+    # Gallery membership is keyed on the submission's PORTAL, not its
+    # free-form tags (see get_document_list) — query by the portal id.
+    response = client.get("/api/documents/list?tags=test-portal")
     assert response.status_code == 200
     data = response.json()
     assert len(data) > 0