Seeding is broken in dev environment due to failed SQLALCHEMY_DATABASE_URI sourcing

After #86 (closed) being fixed here is another error in our dev setup I get:

tor_weather_seeder | Traceback (most recent call last):
tor_weather_seeder |   File "/usr/local/lib/python3.10/runpy.py", line 196, in _run_module_as_main
tor_weather_seeder |     return _run_code(code, main_globals, None,
tor_weather_seeder |   File "/usr/local/lib/python3.10/runpy.py", line 86, in _run_code
tor_weather_seeder |     exec(code, run_globals)
tor_weather_seeder |   File "/app/scripts/seed.py", line 68, in <module>
tor_weather_seeder |     db_session = get_db_session()
tor_weather_seeder |   File "/app/scripts/seed.py", line 33, in get_db_session
tor_weather_seeder |     raise AssertionError("SQLALCHEMY_DATABASE_URI environment variable not set")
tor_weather_seeder | AssertionError: SQLALCHEMY_DATABASE_URI environment variable not set
tor_weather_seeder exited with code 1

It seems we have an issue with source ./deployment/dev/.env in our seed-data.sh script. Following the approach in our startup-script.sh script seems to work around that, though.