Build checkout and save a pending order

Context: this project is the online store "Thread & Needle", a fashion e-commerce store that sells women's and men's clothing, shoes and accessories to customers mainly in United States and charges in USD. It uses Next.js (App Router), TypeScript, Tailwind CSS, PostgreSQL with Drizzle ORM (local database shop_local), Zod and Auth.js. Product pages, images, the cart and customer accounts already exist from earlier episodes.

Goal: build the checkout and save a pending order. Do NOT take payment yet. The payment gateway (Stripe) is connected in the next episode.

Plan first: read the project, then show me your plan (files to add or change, new database tables) and wait for my OK before changing anything. Explain any technical word in a few plain words.

Tasks, after I approve:
1. Database (Drizzle migration, applied only to shop_local): add orders, order_items and, for signed-in customers, saved addresses. Store all money as whole numbers in the smallest currency unit (for example cents), never as decimals. An order holds: an order number, status (starts as pending), customer email, optional user id, currency, subtotal, shipping, tax, total, a copy of the shipping address, a copy of the chosen shipping method, and created time. Each order item holds a copy of the product name, variant, unit price, quantity and image at the time of purchase, so later edits to the catalogue never change old orders.
2. Checkout page: contact email, shipping address (use the fields and postcode format that fit United States), shipping option, and an order summary. Signed-in customers get their saved address prefilled. Guests can check out without an account if I confirm it.
3. Shipping options: keep two or three options in one config file, with placeholder prices in USD and an optional free-shipping threshold. Mark them clearly as placeholders I must confirm.
4. Tax placeholder: one function that returns tax for an order. For now it returns zero and the page says tax is not yet calculated. Do not claim any tax compliance; tell me this is a decision for me and a tax adviser.
5. Server-side pricing: write one function that rebuilds the cart from the database and computes every total. It must ignore any price, total or shipping cost sent from the browser. It must reject unpublished products, missing variants, quantities below 1 or above a sensible limit, and quantities that exceed stock.
6. Place-order action: validate all input with Zod, apply a simple rate limit, recompute totals, then create the order and its items in one database transaction. Generate a readable order number from a short store prefix plus a database sequence. Redirect to a "pending order" page. Guests may view their order only with a long random access token; store only its hash.

Security rules: never trust prices or ids from the browser; check that a signed-in customer can only read their own orders; do not log full addresses; never print, log or commit any secret; only use names in .env.example.

Verify yourself and show me the results: write Vitest tests for the pricing function (tampered price, negative quantity, unpublished product, out-of-stock item, free-shipping threshold), then run the tests, the type check and the linter. Start the site and place one test order from the cart, then show me the order rows in shop_local.

Commit to a new branch named feature/checkout-orders with a clear message.

Report back in this format: 1) What was done. 2) What I should check in the browser. 3) Anything that needs my decision (shipping prices, tax, guest checkout).

Review the prompt, then copy it. Never paste real passwords or API keys into a chat.