[codex] fix(inventory): handle string order status on receive

[robotlearning123]

Summary

Fix receive_items() so it handles order statuses loaded back from the database as plain strings instead of assuming an enum instance.

Root Cause

Order.status is stored as a string field. In a fresh session, SQLModel returns values like "received" as str, but receive_items() called order.status.value in the already-received/cancelled/deleted guard. That raised AttributeError instead of the intended ValidationError.

What Changed

• Normalize the blocked-status label with getattr(order.status, "value", order.status) before building the validation message.
• Add a regression test that commits the first receive, opens a new session, and verifies the second receive is rejected cleanly after reload.

Impact

• Prevents a 500-class crash when a receive request hits an order already marked received in a prior transaction.
• Preserves the intended user-facing validation behavior without changing any happy-path inventory logic.

Validation

• uv run pytest -q tests/test_inventory_service_coverage.py -k 'receive'