bootstrap: fix minor issues with profile picture cropping

* Add required [1] "display: block;" style property to img element
* Fix image overflow in modal. As cropper size inherits from img's parent element [2] (including padding according to my research), we need to wrap modal body into another div that has the padding we want.
* Remove ability [3] to click away to dismiss the modal as it often interfered with user interaction when cropping.

[1] https://github.com/fengyuanchen/cropperjs/tree/v1?tab=readme-ov-file#example
[2] https://github.com/fengyuanchen/cropperjs/tree/v1?tab=readme-ov-file#notes
[3] https://getbootstrap.com/docs/4.0/components/modal/#options



Signed-off-by: Alexis Mercier des Rochettes <apernouille@gmail.com>