feat(ci): retry dep-PR container verification until publish lands

The post-merge dep-PR step races the producer's image-build workflow
and fails 404 before the tag is pushed. resolve_container_digest gains
a timeout_s retry (15s interval); --verify-timeout exposes it
(default 600s).

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

tests/unit/test_create_dependency_pr.py

@@ -621,3 +621,24 @@ class TestBranchCreation:
         # PR title carries the task ID
         assert client.create_pr.call_args.kwargs["title"] == "OBL-INFRA-581: Bump sso_bridge to 0.9.1"
         mock_task.assert_called_once()
+
+    def test_retries_404_until_published(self) -> None:
+        import requests
+
+        from devx.ci.create_dependency_pr import resolve_container_digest
+
+        err = requests.HTTPError("404")
+        err.response = MagicMock(status_code=404)
+        fail = MagicMock()
+        fail.raise_for_status.side_effect = err
+        ok = MagicMock()
+        ok.raise_for_status = MagicMock()
+        ok.json.return_value = [{"name": "manifest.json", "sha256": "cafe"}]
+        with (
+            patch("devx.ci.create_dependency_pr.requests.get", side_effect=[fail, ok]),
+            patch("devx.ci.create_dependency_pr.time.sleep"),
+        ):
+            digest = resolve_container_digest(
+                "https://git.example.com/api/v1", "oblachno", "sso-bridge", "0.9.1", "tok", timeout_s=60
+            )
+        assert digest == "sha256:cafe"