Lays the Python-side groundwork for the phone companion app's eventual
log sync (Milestone 0 of the diet-app-as-wise-balloon plan):
- log_meal() stamps every entry with a UUID id for union-by-id merging
across devices.
- undo_last_today() now tombstones (deleted: true, re-signed) instead of
popping the entry, so a sync merge can't resurrect a stale copy of
something already undone on another device.
- log_meal() accepts components, the full per-item macros for a
composite meal, so a food bank rebuilt purely by replaying the log can
recover every component's standalone nutrition.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FU3f5KQ1GHXsbbSecfVEyF