Form modal standardization

Implemented the following:

1) Addressed comments in PR #71 including:

the anonymous field for forum posts is now stored as booleans
HTML from text editor now sanitized using DOMPurify before being displayed
likes are calculated solely based off the list of likers
all confirmTask and confirmRepeateable logic (handling single and multiple confirmations) have been abstracted to single functions called confirmTasks and confirmRepeatables in mutations.ts

2) Form fixes

All forms should submit upon hitting enter and be wrapped around a Box component='form'.

3) Modal fixes

All modals should now be implemented using the MUI Dialog component.
TeacherModalStyled in TaskModalSytles.tsx are now extended with the Dialog component. TaskModalBox has been changed to TaskModalContent (and extended with DialogContent). StudentTaskModalBox has also been extended with DialogContent.
ModalTitle has been changed to use DialogTitle and consists of a Stack including the title and a cancel icon.
Note that TeacherModalStyled, TaskModalContent, and StudentTaskModalBox are currently implemented to be identical to Dialog and DialogContent, but were kept if we decide to add more specific styling down the line.

hcs-t4sg / questable