docs: architecture, guidelines, domain designs, progressive code index

docs/code_index/order.md

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+# Index: Order & Freight
+
+Domain design: `docs/domains/orders.md`. Specs: `openspec/specs/order/`,
+`shipment/`, `shipping/`.
+
+## Backend (`apps/api`)
+
+| File | Holds |
+|---|---|
+| `src/modules/order/service.rs` | checkout transaction, pay/cancel, shipping quote |
+| `src/modules/order/repo.rs` | `ORDER_COLS`/`ORDER_ITEM_COLS`, insert_order/insert_item, locks, status transitions |
+| `src/modules/order/handlers.rs` | `/orders*` customer routes, `/shop/orders*`, `/admin/orders` |
+| `src/modules/order/dto.rs` | OrderView, AddressBody, ShippingQuoteView |
+| `src/modules/fulfillment/` | shipments: create (company-validated), ship, confirm-delivered |
+| `src/modules/freight/service.rs` | template CRUD, region rules, `shop_fee()` calculation, company dictionary |
+| `src/modules/freight/handlers.rs` | `/shop/freight-templates*`, `/shipping/companies` |
+| `migrations/0004_orders.sql` | orders/order_items/shipments base schema |
+| `migrations/0017_freight_templates.sql` | freight tables, `orders.shipping_fee_minor`, item snapshots, `skus.weight_grams` |
+| `tests/orders.rs`, `tests/freight.rs` | integration coverage |
+
+## Shared contract (`packages/shared/src`)
+
+`types.ts`: `Order`, `OrderItem`, `Shipment`, `FreightTemplate*`,
+`ShippingCompany`, `ShippingQuote`. `api.ts`: `checkout`, `quoteShipping`,
+`listShippingCompanies`, shop freight CRUD, `createShipment`.
+
+## Frontends
+
+- Mall: `pages/checkout/{index,pay,success}.vue`, `pages/user/orders/`,
+  `pages/user/addresses.vue`
+- Shop-admin: `pages/orders/`, `pages/shipments.vue`,
+  `pages/freight-templates.vue`, `components/ProductForm.vue`
+  (freight template + SKU weight)
+- Admin: `pages/orders.vue` (read-only)