Phase 7 Exact-Head Checkpoint Validation

The commit containing this record is the final Phase 7 validation candidate for PR #29.

The permanent backend and Android workflow files differ from their normal definitions only by a checkpoint comment. Their jobs, permissions, path filters, toolchains and validation steps remain unchanged.

The candidate must pass backend, Android, operations-portal and documentation workflows on one exact head before merge. Exact run numbers and artifact digests are recorded in the PR completion record and the post-merge stable checkpoint record.

Phase 8 remains unclaimed and unauthorized. Real data, production credentials, storage, maps, messaging, payments, deployment and public pilot operation remain outside this checkpoint.