feat: 依存エンティティのFKにOnDelete CASCADEを追加

[devin-ai-integration]

変更点

親エンティティ削除時に、それに依存する子・中間テーブルのレコードが取り残されないよう、GORM モデル（internal/shared/model）の外部キー制約に OnDelete:CASCADE を追加した。マイグレーションファイルは含めない（別途 mise run migrate:diff で生成する運用）。

追加した OnDelete:CASCADE（いずれも従属関係・中間テーブル）:

• Subject 配下の詳細/子テーブル: cancelled_classes, makeup_classes, room_changes, timetable_items, subject_eligible_attributes, subject_requirements, subject_faculties (subject_id)
• 中間テーブルの両辺:
  • course_registrations → subjects, users
  • faculty_rooms → faculties, rooms
  • subject_faculties → faculties
  • timetable_item_rooms → timetable_items, rooms

意図的に CASCADE を付けなかったもの:

• subjects.syllabus_id → syllabuses: シラバスは Subject のマスタ的参照であり、削除で Subject 連鎖削除は過剰なため NO ACTION のまま
• room_changes.original_room_id / new_room_id → rooms: rooms はマスタデータの参照であり、削除時に room_changes を消すのは不適切なため NO ACTION のまま

なお fcm_tokens → users, notification_target_users → notifications/users は既に CASCADE 済み。

確認

• go build ./... / go vet ./... / gofmt -l . OK

Link to Devin session: https://app.devin.ai/sessions/7b2fcdbd708e410aadf9035ff7dcaf0d
Requested by: @kantacky

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View logs

[devin-ai-integration]

Original prompt from Kanta

SYSTEM:
=== BEGIN THREAD HISTORY (in #times_kantacky) ===
<most_recent_message>
Kanta Oikawa (U071TQ4TLTB): @Devin
fun-dotto/server で、OnDelete CASCADEが必要そうなところには追加して
</most_recent_message>
=== END THREAD HISTORY ===

Thread URL: https://furarico.slack.com/archives/C08DF8VMA8N/p1783509227547529?thread_ts=1783509227.547529&amp;cid=C08DF8VMA8N

The latest message is the one right above that tagged you. The <most_recent_message> is the message that you should use to guide your goals + task for this session, and you should use the rest of the slack thread as context.

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