fix(nspd-sync): address PR #111 auto-review M1-M5+M7 findings

M1 (runtime bug): remove WHERE region_code from outer cad_quarters_geom SELECT
in harvest_stale_quarters — column does not exist in prod schema
(cad_number, geom, raw_props, fetched_at, source). Would crash on first beat
tick. Inner nspd_quarter_dumps subquery keeps region_code filter unchanged.

M2 (correctness): _upsert_dump теперь делает db.rollback() в except перед
db.close() — prevents PendingRollbackError на следующем session use, если
PostGIS отбракует geometry или JSON cast failure.

M3 (low): worker_ready breadcrumb INSERT тоже теперь имеет rollback —
consistency с остальными session usages в celery_app.py.

M4 (style): layers_fetched — заменил manual string concat
'{' + ','.join(...) + '}' на native Python list. psycopg v3 сам сериализует
list → text[]. Защита от future layer names с запятыми/фигурными скобками.

M5 (style): import datetime as _dt поднят из else branch в top-level imports.

M7 (test cleanup): удалил dead __enter__/__exit__ mock setup в
test_harvest_stale_quarters_fanout / _empty. harvest_stale_quarters не
использует session как context manager — moc'и no-op.

14/14 tests pass. ruff/format clean.

Per auto-review on 9b2a289.

backend/app/workers/celery_app.py

@@ -302,6 +302,9 @@ def _resume_zombie_runs(sender=None, **_kwargs) -> None:
                 )
             )
             _db.commit()
+        except Exception:
+            _db.rollback()
+            raise
         finally:
             _db.close()
     except Exception as _e:

backend/app/workers/tasks/nspd_sync.py

@@ -18,6 +18,7 @@ UPSERT pattern:
 
 from __future__ import annotations
 
+import datetime as _dt
 import json
 import logging
 import time
@@ -179,7 +180,7 @@ def _upsert_dump(
                 "risks_count": _build_risks_count(dump),
                 "total_features": dump.total_features,
                 "features_json": json.dumps(features_json or [], ensure_ascii=False),
-                "layers_fetched": "{" + ",".join(dump.layers_fetched) + "}",
+                "layers_fetched": list(dump.layers_fetched),
                 "fetched_at_utc": dump.fetched_at_utc,
                 "harvest_duration_ms": duration_ms,
                 "harvest_error": harvest_error,
@@ -187,8 +188,6 @@ def _upsert_dump(
             }
         else:
             # Error-only row: нулевые счётчики, harvest_error filled
-            import datetime as _dt
-
             params = {
                 "quarter_cad": quarter_cad,
                 "geom_json": None,
@@ -205,7 +204,7 @@ def _upsert_dump(
                 "risks_count": 0,
                 "total_features": 0,
                 "features_json": "[]",
-                "layers_fetched": "{}",
+                "layers_fetched": [],
                 "fetched_at_utc": _dt.datetime.now(_dt.UTC).isoformat(),
                 "harvest_duration_ms": duration_ms,
                 "harvest_error": harvest_error,
@@ -214,6 +213,9 @@ def _upsert_dump(
 
         db.execute(_UPSERT_SQL, params)
         db.commit()
+    except Exception:
+        db.rollback()
+        raise
     finally:
         db.close()
 
@@ -360,8 +362,7 @@ def harvest_stale_quarters(
                 """
                 SELECT cad_number
                   FROM cad_quarters_geom
-                 WHERE region_code = :rc
+                 WHERE cad_number NOT IN (
-                   AND cad_number NOT IN (
                        SELECT quarter_cad
                          FROM nspd_quarter_dumps
                         WHERE region_code = :rc

backend/tests/test_nspd_sync.py

@@ -296,8 +296,6 @@ def test_harvest_stale_quarters_fanout(
     # Mock DB session
     mock_db = MagicMock()
     mock_session_cls.return_value = mock_db
-    mock_db.__enter__ = MagicMock(return_value=mock_db)
-    mock_db.__exit__ = MagicMock(return_value=False)
     mock_db.execute.return_value.all.return_value = [(c,) for c in stale_cads]
 
     # harvest_quarter.apply_async — проверяем что вызван для каждого cad
@@ -324,8 +322,6 @@ def test_harvest_stale_quarters_empty(
     """Нет stale кварталов → 0 enqueued, apply_async не вызван."""
     mock_db = MagicMock()
     mock_session_cls.return_value = mock_db
-    mock_db.__enter__ = MagicMock(return_value=mock_db)
-    mock_db.__exit__ = MagicMock(return_value=False)
     mock_db.execute.return_value.all.return_value = []
 
     mock_task.apply_async = MagicMock()