[Feature] better ENV var handling

[mmomjian]

I have searched the existing feature requests to make sure this is not a duplicate request.

• Yes

The feature

• immich_server should fail to start if either DB_URL or DB_username/password/database_name is not passed. Should also fail to start if both URL and the latter are provided, as this is not intended
• immich_server should log a WARNING if TZ is not set

Platform

• Server
• Web
• Mobile