refactor: 重构 AgentScope ReAct Runner 与事件处理

- 重构 runtime/runner.py 实现 ReAct Agent 核心逻辑
- 更新事件编码器与存储机制
- 优化 prompt 系统与 tool 调用
- 调整 agent service 与 repository 配合

backend/src/v1/users/repository.py

@@ -23,6 +23,10 @@ class UserRepository(Protocol):
         """Get user by user ID."""
         ...
 
+    async def get_by_user_ids(self, user_ids: list[UUID]) -> dict[UUID, Profile]:
+        """Batch get users by user IDs."""
+        ...
+
     async def get_by_username(self, username: str) -> Profile | None:
         """Get user by username."""
         ...
@@ -57,6 +61,25 @@ class SQLAlchemyUserRepository(BaseRepository[Profile]):
             logger.exception("User lookup failed", user_id=str(user_id))
             raise
 
+    async def get_by_user_ids(self, user_ids: list[UUID]) -> dict[UUID, Profile]:
+        if not user_ids:
+            return {}
+        try:
+            unique_ids = list(dict.fromkeys(user_ids))
+            stmt = (
+                select(Profile)
+                .where(Profile.id.in_(unique_ids))
+                .where(Profile.deleted_at.is_(None))
+            )
+            result = await self._session.execute(stmt)
+            profiles = list(result.scalars().all())
+            return {profile.id: profile for profile in profiles}
+        except SQLAlchemyError:
+            logger.exception(
+                "Batch user lookup failed", user_ids=[str(i) for i in user_ids]
+            )
+            raise
+
     async def get_by_username(self, username: str) -> Profile | None:
         try:
             stmt = (