refactor: enhance code comments for clarity and maintainability across multiple files

backend/app/services/board_snapshot.py

@@ -149,6 +149,8 @@ async def build_board_snapshot(session: AsyncSession, board: Board) -> BoardSnap
         approval_ids=approval_ids,
     )
     task_title_by_id = {task.id: task.title for task in tasks}
+    # Hydrate each approval with linked task metadata, falling back to legacy
+    # single-task fields so older rows still render complete approval cards.
     approval_reads = [
         _approval_to_read(
             approval,

backend/app/services/organizations.py

@@ -175,6 +175,8 @@ async def accept_invite(
     session.add(member)
     await session.flush()
 
+    # For scoped invites, copy invite board-access rows onto the member at accept
+    # time so effective permissions survive invite lifecycle cleanup.
     if not (invite.all_boards_read or invite.all_boards_write):
         access_rows = list(
             await session.exec(

backend/app/services/task_dependencies.py

@@ -164,7 +164,8 @@ async def validate_dependency_update(
             },
         )
 
-    # Ensure the dependency graph is acyclic after applying the update.
+    # Rebuild the board-wide graph and overlay the pending edit for this task so
+    # validation catches indirect cycles created through existing edges.
     task_ids = list(
         await session.exec(
             select(col(Task.id)).where(col(Task.board_id) == board_id),