Add a .dockerignore that whitelists only requirements.txt, start.py and
dsc/. The build context previously included .git, .idea, __pycache__ and
any local .env, which slowed builds and put a secrets file within reach
of any future COPY of the whole tree.
Remove the unused urlparse import from dsc/client.py and the redundant
import os.path from start.py; importing os already binds os.path.
Record both in IMPROVEMENTS.md, including the part still outstanding:
binutils and squashfs-tools remain in the runtime image because the
AppImage is unpacked in the same stage.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
