feat(storage): enhance storage package with async provider and docs

Add to packages/storage/:
- README.md and README_zh.md - comprehensive documentation
- store/persistence/async_provider.py - async persistence provider

Update repositories:
- contracts/thread_meta.py - add new contract method
- db/thread_meta.py - implement new method
- factory.py - update factory logic

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/packages/storage/store/repositories/contracts/thread_meta.py

@@ -39,6 +39,7 @@ class ThreadMetaRepositoryProtocol(Protocol):
         self,
         thread_id: str,
         *,
+        assistant_id: str | None = None,
         display_name: str | None = None,
         status: str | None = None,
         metadata: dict[str, Any] | None = None,

backend/packages/storage/store/repositories/db/thread_meta.py

@@ -49,11 +49,14 @@ class DbThreadMetaRepository(ThreadMetaRepositoryProtocol):
             self,
             thread_id: str,
             *,
+            assistant_id: str | None = None,
             display_name: str | None = None,
             status: str | None = None,
             metadata: dict[str, Any] | None = None,
     ) -> None:
         values: dict = {}
+        if assistant_id is not None:
+            values["assistant_id"] = assistant_id
         if display_name is not None:
             values["display_name"] = display_name
         if status is not None:

backend/packages/storage/store/repositories/factory.py

@@ -6,7 +6,12 @@ from store.repositories import (
     RunRepositoryProtocol,
     ThreadMetaRepositoryProtocol,
 )
-from store.repositories.db import DbFeedbackRepository, DbRunEventRepository, DbRunRepository, DbThreadMetaRepository
+from store.repositories.db import (
+    DbFeedbackRepository,
+    DbRunEventRepository,
+    DbRunRepository,
+    DbThreadMetaRepository,
+)
 
 
 def build_thread_meta_repository(session: AsyncSession) -> ThreadMetaRepositoryProtocol: