Sync menu for an outlet

Sync a full menu for a specific outlet. The outlet is identified by `{outletId}` (store UUID). The POS adapter resolves its own store identifier to the outlet UUID before calling this endpoint. The request body is a **JSON array** of menu objects (one outlet can have multiple menus, e.g. delivery menu + pickup menu). The endpoint processes synchronously within a single transaction: upserts menus, items, modifiers, bundle sections, operating hours, and store links. **Idempotent:** calling with the same payload again updates existing records.