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>

vitest.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+    include: ['tests/**/*.test.ts'],
+    testTimeout: 60_000,
+    hookTimeout: 60_000,
+  },
+  resolve: {
+    alias: {
+      '#': new URL('./src', import.meta.url).pathname,
+    },
+  },
+})