refactor: streamline imports and clean up group access handling in board-related files

backend/app/api/board_groups.py

@@ -271,7 +271,7 @@ async def delete_board_group(
     session: AsyncSession = Depends(get_session),
     ctx=Depends(require_org_admin),
 ) -> OkResponse:
-    group = await _require_group_access(session, group_id=group_id, member=ctx.member, write=True)
+    await _require_group_access(session, group_id=group_id, member=ctx.member, write=True)
 
     # Boards reference groups, so clear the FK first to keep deletes simple.
     await session.execute(

backend/app/api/board_memory.py

@@ -6,7 +6,7 @@ from collections.abc import AsyncIterator
 from datetime import datetime, timezone
 from uuid import UUID
 
-from fastapi import APIRouter, Depends, HTTPException, Query, Request, status
+from fastapi import APIRouter, Depends, Query, Request
 from sqlalchemy import func
 from sqlmodel import col, select
 from sqlmodel.ext.asyncio.session import AsyncSession

backend/app/services/organizations.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from datetime import datetime
 from typing import Iterable
 from uuid import UUID