feat: add CI, Docker, auth, typed API client, shiki code blocks, e2e tests

- CI: GitHub Actions (bun 1.3.14, lint/typecheck/test/build/format gates)
- Docker: multi-stage standalone build + .dockerignore (next.config output=standalone)
- Auth: better-auth server (memory adapter, drizzle-swap-ready) + react client
  + /api/auth/[...all] route handler
- API: /api/health + /api/openapi routes, openapi-typescript codegen to
  types/api.ts, typed openapi-fetch client (lib/api, lib/http)
- Shiki: server-side CodeBlock component (escaped HTML)
- E2E: playwright home + health specs on dedicated :3100 (chromium 1243
  installed from GCS after CDN timeout)
- Dev: allow 127.0.0.1/localhost dev origins (HMR for local tooling)

next.config.ts

@@ -1,5 +1,10 @@
 import type { NextConfig } from "next";
 
-const nextConfig: NextConfig = {/* config options here */};
+const nextConfig: NextConfig = {
+  output: "standalone",
+  // Allow HMR/dev resources for local tooling (Playwright webServer on 127.0.0.1,
+  // LAN dev access). Only affects `next dev`.
+  allowedDevOrigins: ["127.0.0.1", "localhost"],
+};
 
 export default nextConfig;