The v0.1.1 tag failed to publish anything. Only the app-facing package was
bumped, which broke both workflows: CI's version-lockstep gate rejected the
0.1.0/0.1.1 mix, and the publish job aborted on its first step because
attested_secure_keys_platform_interface was still 0.1.0, a version pub.dev
already has.

Bump the platform interface and the two implementation packages to 0.1.1 so
the set is back in lockstep. No code or API changes in any of them.

Also guard each publish step with .github/scripts/publish-if-new.sh, which
skips a package whose version is already on pub.dev. `dart pub publish`
treats that case as a hard error, so a re-run after a partial release would
otherwise keep dying on the packages that already uploaded.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>