Can I vibe code Fulfil.io?

Build a robust Python/FastAPI microservice for multi-location inventory and purchase order management designed for a D2C ecommerce brand.

1. DATA MODEL:
- Implement PostgreSQL models using SQLModel or SQLAlchemy.
- `Item`: sku (unique), name, barcode, weight, unit_cost.
- `Warehouse`: id, name, code.
- `Location`: id, warehouse_id, code (e.g., A-01-B), type (storage, picking, receiving, transit).
- `StockQuant`: item_id, location_id, qty_on_hand, qty_reserved, lot_number.
- `InventoryMove`: id, item_id, from_location_id, to_location_id, qty, state (draft, assigned, done), cost_unit, created_at.
- `PurchaseOrder` and `PurchaseOrderLine`: supplier details, expected delivery date, landed_cost_extra (shipping/duties).

2. CORE FUNCTIONALITY:
- Order Reservation: Expose an API endpoint `POST /api/v1/reserve` that accepts an order with multiple SKUs. Use PostgreSQL `SELECT FOR UPDATE` row-level locking to prevent race conditions during inventory deduction.
- FIFO Stock Allocation: When an order is reserved, allocate stock from picking locations using First-In-First-Out logic based on stock lot creation date.
- PO Receiving & Landed Cost: Implement a PO receipt workflow. When goods are received, calculate the updated unit cost as `unit_cost + (landed_cost_extra * (line_subtotal / total_po_subtotal) / line_qty)` and generate an `InventoryMove` into the receiving location.
- Multi-Channel Sync: Webhook handler for Shopify `orders/create` that automatically initiates stock reservation and emits a websocket event to updated UI clients.

3. FAILURE MODES & TRANSACTIONS:
- Wrap all inventory movements inside strict database transactions. If stock is insufficient for any line item, rollback the entire transaction and raise a `409 Conflict` with exact unfillable SKUs.
- Handle negative inventory states gracefully by blocking movements from storage locations if `qty_on_hand - qty_reserved < requested_qty`.

4. OUT OF SCOPE:
- Full GAAP double-entry general ledger posting.
- Barcode mobile scanner UI (provide standard JSON REST endpoints only).
- Tax filing and payroll automation.

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