将persist和后端分离，方便替换为其他数据库

tests/unit/test_multi_project_pipeline_config.py

@@ -9,7 +9,7 @@ from pydantic import BaseModel
 from sync_state_machine.config.multi_project_config import build_multi_project_config_from_file
 from sync_state_machine.common.binding import BindingManager
 from sync_state_machine.common.collection import DataCollection
-from sync_state_machine.common.persistence import PersistenceBackend
+from sync_state_machine.common.sqlite_backend import SQLitePersistenceBackend
 from sync_state_machine.common.sync_node import SyncNode
 from sync_state_machine.pipeline.multi_project_pipeline import (
     _project_scope_overrides,
@@ -88,7 +88,7 @@ class _ProjectNode(SyncNode[dict]):
 
 @pytest.mark.asyncio
 async def test_binding_manager_prunes_stale_bindings_after_project_scope_cleanup() -> None:
-    persistence = PersistenceBackend(":memory:")
+    persistence = SQLitePersistenceBackend(":memory:")
     await persistence.initialize()
     try:
         local_collection = DataCollection("local", persistence=persistence, auto_persist=False)