feat(memory-api): add memory detail external service APIs

Add external service APIs for memory detail queries
Provides memory data access endpoints for external service integration
Add utility functions for API key user resolution and end_user validation

Modified files:
- api/app/controllers/service/user_memory_api_controller.py
- api/app/core/api_key_utils.py
- api/app/controllers/service/__init__.py

api/app/core/api_key_utils.py

@@ -3,6 +3,12 @@ import secrets
 from typing import Optional, Union
 from datetime import datetime
 
+from sqlalchemy.orm import Session as _Session
+from app.core.error_codes import BizCode as _BizCode
+from app.core.exceptions import BusinessException as _BusinessException
+from app.models.end_user_model import EndUser as _EndUser
+from app.repositories.end_user_repository import EndUserRepository as _EndUserRepository
+
 from app.models.api_key_model import ApiKeyType
 from fastapi import Response
 from fastapi.responses import JSONResponse
@@ -65,3 +71,63 @@ def datetime_to_timestamp(dt: Optional[datetime]) -> Optional[int]:
         return None
 
     return int(dt.timestamp() * 1000)
+
+
+def get_current_user_from_api_key(db: _Session, api_key_auth):
+    """通过 API Key 构造 current_user 对象。
+
+    从 API Key 反查创建者（管理员用户），并设置其 workspace 上下文。
+    与内部接口的 Depends(get_current_user) (JWT) 等价。
+
+    Args:
+        db: 数据库会话
+        api_key_auth: API Key 认证信息（ApiKeyAuth）
+
+    Returns:
+        User ORM 对象，已设置 current_workspace_id
+    """
+    from app.services import api_key_service
+
+    api_key = api_key_service.ApiKeyService.get_api_key(
+        db, api_key_auth.api_key_id, api_key_auth.workspace_id
+    )
+    current_user = api_key.creator
+    current_user.current_workspace_id = api_key_auth.workspace_id
+    return current_user
+
+
+def validate_end_user_in_workspace(
+    db: _Session,
+    end_user_id: str,
+    workspace_id,
+) -> _EndUser:
+    """校验 end_user 是否存在且属于指定 workspace。
+
+    Args:
+        db: 数据库会话
+        end_user_id: 终端用户 ID
+        workspace_id: 工作空间 ID（UUID 或字符串均可）
+
+    Returns:
+        EndUser ORM 对象（校验通过时）
+
+    Raises:
+        BusinessException(USER_NOT_FOUND): end_user 不存在
+        BusinessException(PERMISSION_DENIED): end_user 不属于该 workspace
+    """
+    end_user_repo = _EndUserRepository(db)
+    end_user = end_user_repo.get_end_user_by_id(end_user_id)
+
+    if end_user is None:
+        raise _BusinessException(
+            "End user not found",
+            _BizCode.USER_NOT_FOUND,
+        )
+
+    if str(end_user.workspace_id) != str(workspace_id):
+        raise _BusinessException(
+            "End user does not belong to this workspace",
+            _BizCode.PERMISSION_DENIED,
+        )
+
+    return end_user