BulkAddPantryItems

Wire shape for POST /v1/pantry/items/bulk. Carries 1..MAX_BULK_ITEMS rows; each row carries an ingredient_id plus optional quantity / status / storage / expiry scalars (same shape as {@see PantryItemRequestData}). Each row is validated against the same enum + cap rules at 422 BEFORE the controller dispatches to the repository. Threat model: - MAX_BULK_ITEMS bounds per-call memory + transaction footprint so a hostile bulk-add cannot DoS the worker. - Per-row enum validation rejects payloads that would otherwise hit the storage-layer CHECK constraint and bubble up as a 500.