Implement ordering MVP domain layer per spec (issue #1)

Scaffolds the TanStack Start + Drizzle/Postgres + Better Auth app and
implements the core ordering domain: menu browsing, guest/account order
placement with online payment, per-Order-Item independent cooking and
cancellation, dynamic Machine-Tag pool assignment, and multi-step recipes
(see docs/adr/0001-0003). Adds a guest-access-token / session-based
ownership check on every read/mutation so an order can't be viewed,
cancelled, or picked up by anyone but its owner.

Covered by 14 tests running the domain layer directly against a real,
ephemeral Postgres (testcontainers) — createServerFn couldn't be called
outside a real request context, so tests exercise the domain functions the
server functions thinly wrap instead of the server functions themselves.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

prettier.config.js

@@ -0,0 +1,10 @@
+//  @ts-check
+
+/** @type {import('prettier').Config} */
+const config = {
+  semi: false,
+  singleQuote: true,
+  trailingComma: "all",
+};
+
+export default config;