phase-0: foundation, both apps boot end to end

Monorepo (pnpm workspaces) with two deployable apps and three pure packages.

apps/api (Hono on Node): Zod validated env that fails fast and names the problem,
Kysely factories for SQLite and Postgres chosen by DATABASE_URL scheme, portable
migrations covering the whole SPEC section 5 schema, Better Auth with the four
roles and seeded demo accounts, localized error envelope, /healthz and /readyz,
graceful SIGTERM drain. Dialect specific SQL is confined to the two factories.

apps/web (Next.js App Router): locale routed shell in es and en with a language
switcher, sign in screen, and a runtime /api proxy so the browser only ever sees
one origin and cookies stay first party.

packages/i18n ships both catalogs complete; es is generated from COPY.md and a
test re-derives it from the document on every run so it cannot drift.
packages/contracts holds the Zod schemas and the typed client the web app uses.

Verified: 43 vitest tests, 14 Playwright tests on mobile and desktop, typecheck
and lint clean, migrate and seed from a clean database, sign in through the proxy
with CSRF rejection of foreign origins.

Not verified here: docker compose. This user has no access to the docker socket.

RULES.md is absent from docs/, so packages/rules exports only RULES_VERSION and
no tax rule, check digit or deadline was invented. See DECISIONS.md.

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

apps/web/app/api/[...path]/route.ts

@@ -0,0 +1,68 @@
+import type { NextRequest } from 'next/server';
+
+/**
+ * Single origin proxy: the browser only ever talks to the web origin, and everything
+ * under /api is forwarded to the API container. Cookies stay first party, so there is
+ * no CORS anywhere in v1.
+ *
+ * SPEC-GAP: SPEC.md section 2 specifies Next rewrites for this. Next bakes rewrite
+ * destinations into the build manifest, which would make API_INTERNAL_URL a build time
+ * value and stop one image from running in both compose and k8s. A route handler reads
+ * it per request instead, which is what "all configuration via .env" requires.
+ */
+
+export const dynamic = 'force-dynamic';
+
+/** Set by the proxy or the runtime, never forwarded verbatim. */
+const STRIPPED_REQUEST_HEADERS = new Set([
+  'host',
+  'connection',
+  'content-length',
+  'transfer-encoding',
+  'accept-encoding',
+]);
+
+const STRIPPED_RESPONSE_HEADERS = new Set(['content-encoding', 'content-length', 'transfer-encoding']);
+
+function apiBaseUrl(): string {
+  return (process.env['API_INTERNAL_URL'] ?? 'http://localhost:4000').replace(/\/$/, '');
+}
+
+async function proxy(request: NextRequest): Promise<Response> {
+  const incoming = new URL(request.url);
+  const target = `${apiBaseUrl()}${incoming.pathname}${incoming.search}`;
+
+  const headers = new Headers();
+  request.headers.forEach((value, key) => {
+    if (!STRIPPED_REQUEST_HEADERS.has(key.toLowerCase())) headers.set(key, value);
+  });
+
+  const hasBody = request.method !== 'GET' && request.method !== 'HEAD';
+  const upstream = await fetch(target, {
+    method: request.method,
+    headers,
+    redirect: 'manual',
+    ...(hasBody ? { body: request.body, duplex: 'half' } : {}),
+  } as RequestInit & { duplex?: 'half' });
+
+  const responseHeaders = new Headers();
+  upstream.headers.forEach((value, key) => {
+    const name = key.toLowerCase();
+    if (name === 'set-cookie') return;
+    if (!STRIPPED_RESPONSE_HEADERS.has(name)) responseHeaders.set(key, value);
+  });
+  // Session and CSRF cookies arrive as several Set-Cookie headers and must stay separate.
+  for (const cookie of upstream.headers.getSetCookie()) {
+    responseHeaders.append('set-cookie', cookie);
+  }
+
+  return new Response(upstream.body, { status: upstream.status, headers: responseHeaders });
+}
+
+export const GET = proxy;
+export const POST = proxy;
+export const PUT = proxy;
+export const PATCH = proxy;
+export const DELETE = proxy;
+export const HEAD = proxy;
+export const OPTIONS = proxy;