fix(orders): enforce lifecycle transitions and one-time inventory restoration

[khaira777]

Summary

Order status changes and item cancellation/restore paths do not enforce a transition matrix or one-time inventory adjustment. Repeated terminal requests and void-adjustment rows can make inventory and order state diverge.

Current behavior

• main/routes/orders.ts:806-925 accepts listed target statuses without validating the current-to-target transition.
• Repeating status=cancelled on an already-cancelled order can execute the inventory-restoration loop again.
• Whole-order cancellation includes rows that represent void adjustments.
• The S6-targeted path in main/routes/index.ts:251-508 has similar cancel/restore status and inventory assumptions.

Expected behavior

Order lifecycle transitions should be explicit and monotonic unless a documented adjustment flow is used. Inventory should be restored at most once and only for quantities that were actually deducted.

Acceptance criteria

• Define and enforce a current-to-target transition matrix, including terminal states.
• Re-read order/item state inside the transaction and make repeated requests safe.
• Exclude void_adjustment and already-processed rows from inventory restoration.
• Ensure whole-order cancellation and item cancellation/restore cannot create duplicate adjustments.
• Add tests for repeated cancellation, completed/cancelled sources, voided items, and concurrent requests.

Relevant files

main/routes/orders.ts, main/routes/index.ts, main/routes/order-items.ts