feat(memory-gateway): 引入 Memory Gateway 配置、凭据存储和服务编排

* 新增 MemoryGatewayConfig 和 MemoryConfig dataclass，用于配置管理。
* 实现 MemoryGatewayUserCredential 和 MemoryGatewayCredentialStore，用于处理用户凭据。
* 创建 MemoryGatewayService，用于管理与 Memory Gateway 的交互。
* 开发用于记忆设置的 JSON 配置文件。
* 增强单元测试，覆盖新功能，包括凭据存储和服务行为。
* 更新 entrypoint 和实例创建脚本，以初始化 Memory Gateway 用户存储。

app-instance/backend/beaver/engine/loop.py

@@ -227,6 +227,7 @@ class AgentLoop:
         session_id: str | None = None,
         source: str = "direct",
         user_id: str | None = None,
+        gateway_user_id: str | None = None,
         title: str | None = None,
         execution_context: str | None = None,
         skill_selection_context: str | None = None,
@@ -279,6 +280,7 @@ class AgentLoop:
             session_id=session_id,
             source=source,
             user_id=user_id,
+            gateway_user_id=gateway_user_id,
             title=title,
             execution_context=execution_context,
             skill_selection_context=skill_selection_context,
@@ -319,6 +321,7 @@ class AgentLoop:
         session_id: str | None = None,
         source: str = "direct",
         user_id: str | None = None,
+        gateway_user_id: str | None = None,
         title: str | None = None,
         execution_context: str | None = None,
         skill_selection_context: str | None = None,
@@ -360,6 +363,13 @@ class AgentLoop:
         """
 
         loaded = self.boot()
+        memory_gateway_service = None
+        gateway_credential_store = getattr(loaded, "memory_gateway_credentials", None)
+        gateway_service_factory = getattr(loaded, "memory_gateway_service_factory", None)
+        if gateway_user_id and gateway_credential_store is not None and gateway_service_factory is not None:
+            gateway_credential = gateway_credential_store.get(gateway_user_id)
+            if gateway_credential is not None:
+                memory_gateway_service = gateway_service_factory(gateway_credential)
         session_manager = self._require_loaded("session_manager")
         memory_service = self._require_loaded("memory_service")
         context_builder = self._require_loaded("context_builder")
@@ -482,7 +492,6 @@ class AgentLoop:
         final_model: str | None = resolved_model
         run_started_at = self._utc_now()
         activated_receipts: list[SkillActivationReceipt] = []
-        memory_gateway_service = getattr(loaded, "memory_gateway_service", None)
         try:
             bundle = provider_bundle or make_provider_bundle(
                 model=resolved_model,