Last week summary and reports history don't work once semester ends

[cbrxyz]

Attempting to run events that require an active report history, like last_week_summary or the Reports History button now break because the semester has finished. ATtempting to run these things will produce an error like so:

Traceback (most recent call last):
  File "/usr/local/lib/python3.11/dist-packages/discord/ui/view.py", line 427, in _scheduled_task
    await item.callback(interaction)
  File "/home/cameron/discord-bot/src/reports.py", line 617, in callback
    week = WeekColumn.current()
           ^^^^^^^^^^^^^^^^^^^^
  File "/home/cameron/discord-bot/src/reports.py", line 118, in current
    return cls.from_date(datetime.date.today())
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/cameron/discord-bot/src/reports.py", line 94, in from_date
    col_offset = (date - cls._start_date()).days // 7
                         ^^^^^^^^^^^^^^^^^
  File "/home/cameron/discord-bot/src/reports.py", line 55, in _start_date
    raise RuntimeError("No semester is occurring right now!")
RuntimeError: No semester is occurring right now!

To fix this, these actions should use the previous semester for completing operations.