The tree pins prebuilt_libs_coil at 3.5.0 (coil3.* packages); move the
three image-loading screens to coil3.compose and add coil-network-okhttp
— Coil 3 core ships no network fetcher, so http(s) image URLs need it
(it self-registers through ServiceLoader). Gradle catalog bumped to the
matching io.coil-kt.coil3 coordinates.