Feature/mobile adaptation for canvas

[davideastmond]

This PR addresses mobile issue that affects creating an occurrence on mobile, since dragging is not easily available.

• A date range box appears in the modal pop up allowing the user to pick a date-time
• Calendar canvas updates accordingly
• Added some validation (using zod packages) for dates that are inputted so they are in the correct range
• Also hid the comments section in the modal so user can't create a comment to an occurrence that hasn't yet been created