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/integrations/memory_gateway/__init__.py

@@ -1,5 +0,0 @@
-"""Memory Gateway HTTP integration."""
-
-from .client import MemoryGatewayClient, MemoryGatewayClientError
-
-__all__ = ["MemoryGatewayClient", "MemoryGatewayClientError"]

app-instance/backend/beaver/integrations/memory_gateway/client.py

@@ -1,68 +0,0 @@
-"""Small asynchronous client for the Memory Gateway API."""
-
-from __future__ import annotations
-
-from typing import Any
-
-import httpx
-
-from beaver.foundation.config import MemoryGatewayConfig
-
-
-class MemoryGatewayClientError(RuntimeError):
-    """Sanitized Gateway transport or response failure."""
-
-    def __init__(self, operation: str, category: str, *, status_code: int | None = None) -> None:
-        self.operation = operation
-        self.category = category
-        self.status_code = status_code
-        status = f" status={status_code}" if status_code is not None else ""
-        super().__init__(f"Memory Gateway {operation} failed: {category}{status}")
-
-
-class MemoryGatewayClient:
-    """HTTP transport for search, add, and flush operations."""
-
-    def __init__(
-        self,
-        config: MemoryGatewayConfig,
-        *,
-        transport: httpx.AsyncBaseTransport | None = None,
-    ) -> None:
-        self.config = config
-        self.transport = transport
-
-    async def search(self, payload: dict[str, Any]) -> dict[str, Any]:
-        return await self._post("search", "/memories/search", payload)
-
-    async def add(self, payload: dict[str, Any]) -> dict[str, Any]:
-        return await self._post("add", "/memories/add", payload)
-
-    async def flush(self, payload: dict[str, Any]) -> dict[str, Any]:
-        return await self._post("flush", "/memories/flush", payload)
-
-    async def _post(self, operation: str, path: str, payload: dict[str, Any]) -> dict[str, Any]:
-        try:
-            async with httpx.AsyncClient(
-                base_url=self.config.base_url.rstrip("/"),
-                timeout=self.config.timeout_seconds,
-                transport=self.transport,
-                trust_env=False,
-            ) as client:
-                response = await client.post(path, json=payload)
-                response.raise_for_status()
-                data = response.json()
-        except httpx.HTTPStatusError as exc:
-            raise MemoryGatewayClientError(
-                operation,
-                "http_status",
-                status_code=exc.response.status_code,
-            ) from None
-        except httpx.RequestError:
-            raise MemoryGatewayClientError(operation, "network") from None
-        except ValueError:
-            raise MemoryGatewayClientError(operation, "invalid_json") from None
-
-        if not isinstance(data, dict):
-            raise MemoryGatewayClientError(operation, "invalid_response")
-        return data