feat(assets): update app loader

...ents/structures-list/admin-structures-list.component.html

src/app/app.component.html

.../structure-list-print/structure-list-print.component.html

src/app/post/components/post-list/post-list.component.html

src/assets/gif/loader_circle.gif

src/assets/gif/loader_circle_grey.gif