[BUG][HIGH] Self-schedule end date calculation TypeError and logic bug

[kambiz-aghaiepour]

Description

The self-schedule end date calculation has two bugs:

1. ssm_deadline_hour is a string from config but passed directly to datetime.replace(hour=...) which requires an integer, causing a TypeError.
2. Even if cast to int, if the user requests at 22:00 and the deadline hour is 21:00, days_ahead could be 0, making end before start, causing valid requests to be rejected.

Affected Code

# src/quads/server/blueprints/schedules.py:248-262
ssm_deadline_hour = Config.get("ssm_deadline_hour", "21")  # returns string "21"
end = start.replace(hour=ssm_deadline_hour, minute=0, second=0, microsecond=0) + timedelta(days=days_ahead)

Impact

• TypeError crash when self-scheduling is attempted
• Valid scheduling requests rejected due to end date before start date

Recommended Fix

1. Cast ssm_deadline_hour to int: int(Config.get("ssm_deadline_hour", "21"))
2. Fix the logic to ensure end is always after start, e.g., if computed end < start, advance by one more day.

[sadsfae]

I'm not sure about this, defer to @grafuls