fix: Schedule task on weekends or workweek (#99)

[princ0301]

Fixes #99

What changed

Adds workday and weekend properties to the Job class to allow scheduling tasks on weekdays (Monday-Friday) or weekends (Saturday-Sunday). This is achieved by introducing a weekday_constraints attribute to the Job and updating _schedule_next_run to skip days that do not match the constraint.

Test results

All tests passing after 1 attempt(s).

configfile: pyproject.toml
collected 81 items

test_schedule.py ss.ssss.................sss.ss...................ssssss [ 67%]
ssssssssssssssssssssssss..                                               [100%]

======================== 40 passed, 41 skipped in 0.63s ========================

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