Rewrite Withings to Garmin sync for Docker

[cheungr]

Summary

Replace the legacy multi-destination Python CLI with a focused Withings weight/body-composition sync to Garmin Connect, deployed as a non-root Docker Compose service.

Before

• Large argparse application combined Garmin, TrainerRoad, blood pressure, FIT/JSON export, and Kubernetes/cron deployment surfaces.
• Withings auth required fast manual code pasting, had weak token persistence, and lacked concurrency protection.
• Garmin depended on garth without an interactive MFA path or reliable refreshed-token persistence.

After

• Python 3.12 slim image, Compose scheduler, one ./data volume, configurable UID/GID, healthcheck, and short Ubuntu quickstart.
• garminconnect 0.3.17 with interactive MFA / --mfa-code; Garmin passwords are not persisted and account tokens are saved and refreshed.
• Withings OAuth accepts a code or redirect URL, persists rotated tokens atomically, and sync/state operations use a cross-process lock.
• auth, sync --once, sync --since, and status CLI commands; per-measurement dedup state and UTC FIT body-composition records.
• Remove TrainerRoad, blood pressure, legacy config paths, bundled Withings app credentials, Kubernetes manifests, and the old callback page.
• Add mocked unit tests and CI for tests/Compose build; preserve version-tagged PyPI publishing with a pip/setuptools build.

Validation

• pytest: 10 passed
• docker compose build
• Container --help and status commands