Turn configuration into environment variables

[rui-costa]

Currently MAX_CONCURRENT_JOBS is already configurable, but the remaining configuration is hardcoded.

MAX_CONCURRENT_JOBS = int(os.environ.get("MAX_CONCURRENT_JOBS", "5"))
MAX_FILE_SIZE_MB = 2048  # 2GB limit
JOB_RETENTION_SECONDS = 3600  # 1 hour retention

user should be able to change all depending on their set up

MAX_CONCURRENT_JOBS = int(os.environ.get("MAX_CONCURRENT_JOBS", "5")) # 5 max concurrent if not set
MAX_FILE_SIZE_MB = int(os.environ.get("MAX_FILE_SIZE_MB", "2048")) # 2GB limit if not set
JOB_RETENTION_SECONDS =  int(os.environ.get("JOB_RETENTION_SECONDS", "3600"))  # 1 hour retention if not set