Debian's /bin/sh is dash, which has no history or tab completion. Install
bash + bash-completion, set the mscp user's shell to bash with a minimal
.bashrc, and switch CMD to bash so interactive sessions get line editing.
Add .dockerignore to keep .git and local working dirs out of the build
context and stabilize the COPY . . layer cache.
entrypoint.sh always checked ghcr's :latest manifest for a newer
build, so non-main images (e.g. dev_27) incorrectly reported an
update available since their SHA never matches main's latest. Bake
the image's tag in at build time and check against that tag instead.
