run seed on ci job

**Is your feature request related to a problem? Please describe.**
When the CI environment gets deployed, I currently need to manually run the db_seed.py script against that environment in order to properly test.

**Describe the solution you'd like**
We should have a github action, or something else, run the seed script automatically.

**Describe alternatives you've considered**
I have not given it much thought yet as to where/what can run the script, besides an action.

**Additional context**
None.

まず db_seed.py を見つけ、CI 環境がどのようにデプロイされているかを確認します。その環境に対して GitHub Action が seed スクリプトを実行できる場所を特定し、CI のデプロイ中に手動の介入なしで seeding が自動的に行われれば、issue は完了したものとします。

索引モデルが issue の本文から書いたものです。