Batch publish menus (full-replace)

Publish multiple draft menus to multiple outlets with full-replace semantics.

For each target outlet, this endpoint:

1. Soft-deletes ALL existing live menus for the outlet
2. Creates new live menus from the selected drafts (one per draft per outlet)
3. Records publish logs

Full-replace behavior: Publishing replaces all existing live menus for the target outlets. To keep multiple menus on an outlet, publish them together in one request. One transaction per outlet — if one outlet fails, others may still succeed.