v0.5.5: codex's in-container updater works instead of failing on permissions

codex was installed into npm's default global prefix (/usr), leaving the
package root-owned in /usr/lib/node_modules while the container runs as the
unprivileged aicode user — so `codex update` failed with EACCES. It now
installs under /home/aicode/.local, with /home/aicode/.npmrc pinning the same
prefix across the entrypoint's privilege drop and a /usr/local/bin/codex
symlink keeping the sudo-run init scripts resolving.

Also brings codexbox/pyproject.toml back in step with the tag: it was left at
0.3.5, and the Makefile derives VERSION from it.