fix: modal escape key, timer race, scroll lock

[avinxshKD]

onRequestClose was commented out so Escape never worked. Switched the setTimeout ID from useState to useRef so clearTimeout actually gets the right ID on fast open/close. Added body.overflow hidden/restore so the page doesn't scroll behind the overlay.

Also Cleanup return added to the effect so the timer doesn't fire on unmount.

Fixes #362

[avinxshKD]

@pradeeban as ParentModal is the root of all 9 modals so fixing the 3 bugs here was enough.

[avinxshKD]

Also @pradeeban, wanted to get your take. I'm a little confused between 'CONTROL-CORE usability enhancements' (Project 15) and 'BHV' project(Project 2). As I'm already comfortable in the concore codebase so usability enhancements which is project 15 feels natural for a second project to work on, but I'm also genuinely interested in BHV and familiar with its stack. Since I can only commit to one of them properly alongsight the main concore project, which would you say has more room for learning and more meaningful contribution for gsoc period?
Would really appreciate your guidance :D

[pradeeban]

@avinxshKD Sticking to CONTROL-CORE projects sound more reasonable to me. BHV is crowded with a lot of applicants.