Add array normalization to food API POST endpoint:
- API layer: normalize single object to array (like activity/profile)
- Storage layer: use replaceOne loop with upsert (same as activity pattern)
- Storage layer: accept both single object and array for backward compat
Previously POST /api/food/ with array input would crash:
insertOne([{...}]) → MongoDB error
Now supports both single object and array input consistently.
Response format is now array (matching treatments pattern).
Fixes#8447
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>