Filter invalid time intervals to prevent duplicate Friday records

[val3344]

Remove intervals where begin >= end from lifetimes_map before generating price jobs. This addresses an edge case where closing positions on Fridays could result in duplicate price entries.

The issue stems from the callee's required_daily_prices() function which contains:

for date_begin, date_end in intervals:
    if weekdays_only:
        diff_days = 4 - date_begin.weekday()
        if diff_days < 0:
            date += datetime.timedelta(days=diff_days)

When date_begin == date_end (e.g., when closing positions on Friday), this code would still process the interval and potentially create duplicate Friday records in the price requirements.

By filtering out these invalid intervals at the caller level, we prevent the problematic code path from being executed, ensuring only valid trading periods are processed for price data retrieval.