Prepping for 24sp - Matt <-> Porter handoff

Executive summary of changes:

• undo any changes related to 24wi special calendar of only 9 homeworks
• update calendar & dates (including dummy_days shenanigans), update first day of class in syllabus
• rudimentary 24wi->24sp and 23au->24wi find-and-replace
• replace all homework submission header files to have "Spring 2024"
• undo "end of quarter" disclaimer (prev commit)
• deploy changes to test subdir

Things left to do (between Porter and me)

• "reset content" (when ready - leaving them up for you to peruse)
  • change lectures.yml to have null pre-class, in-class, and resources
  • hide answers to discussion questions
  • comment out urls for homeworks (in projects.yml) to remove them from calendar
  • if keeping search: comment out body of each homework spec file
  • reset commands.yml to only have Week 0 content
• update Porter's bio & office hours
• update TA bios (can be descriptionless for now)
• review syllabus (e.g. you can change the generative AI policy if you'd like)
• change site variables (e.g. EdStem, Gradescope, Canvas, ...)
• adjust references to ItemPool?
• finally, change the variables in 14d5597c to deploy to 24sp subdir instead of test