fix(publish): prompt on sensitive-looking env literals

Replace the "flag any literal env var" check with a key-name heuristic
backed by the upstream DefangLabs keyword detector (password, secret,
token, api_key, …), and convert the hard error into a prompt matching
the existing checkForBindMount / checkForSensitiveData UX. --with-env
silences the env prompt; literal config.content gets its own prompt.

The previous check flagged benign vars like LOG_LEVEL=info, blocking
the 99% case, while still missing low-entropy real secrets the
existing secret-detector skips (MYSQL_ROOT_PASSWORD=toto slips through
on entropy ~1.5).

Refs: docker/compose#13394

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Guillaume Lours <glours@users.noreply.github.com>