Refactor timezones across all containers

[EnigmaCurry]

In the majority of cases, it should be possible to configure docker containers to use a common timezone setting. So we could remove all the TZ env vars from the projects separately, and have a global context TZ instead, inside the main context config:

Technique:

• Always add the TZ env var from the the docker-compose.instance.yaml file, which the Makefile feeds the data, so it could grab TZ from ${ROOT_DIR}/.env_{CONTEXT}.