Migrate logicsrc-web from Vite SPA to Next.js 16 App Router

Replaces the Vite single-page app + custom Node server.js with a Next.js
16.2.6 App Router app.

- proxy.ts (src/proxy.ts): www.logicsrc.com -> logicsrc.com 301 over https,
  preserving path + query (the original request, now via Next 16 Proxy).
- One SSR page via an optional catch-all ([[...slug]]) that renders the same
  marketing/spec page for each known top-level route (/docs, /blog, /openspec,
  ...) and 404s unknown paths, preserving existing canonical URLs. Markup is a
  faithful server-rendered port of the old main.ts (SEO upgrade over the prior
  client render); interactivity (hire-us form, CoinPay button, section scroll)
  moves to a client component.
- API routes ported to app/api/**: hire-us coinpay-checkout + project-request,
  oauth/coinpay start/callback/session, webhooks/coinpay. Shared logic in
  src/lib/coinpay.ts (eligibility, payment-rail selection, webhook verify,
  HMAC session sign/verify, cookies).
- commandboard-api (/health + /api/boards|tasks|plugins/*) is no longer mounted
  in-process; next.config.ts proxies those paths to COMMANDBOARD_API_URL via
  afterFiles rewrites (our own /api routes match first).
- Build/start switch to next build / next start. Contract tests rewritten to
  exercise proxy.ts, the route handlers, and pure helpers directly (21 passing);
  Playwright webServer updated.

Deployment (Railway): set COMMANDBOARD_API_URL to the commandboard-api service
URL and run it as its own service; root start now runs next start.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/logicsrc-web/next.config.ts

@@ -0,0 +1,22 @@
+import type { NextConfig } from "next";
+
+// The CommandBoard API (boards, tasks, plugins, /health) runs as its own
+// service. In the old custom server.js it was mounted in-process; here we proxy
+// those paths to it via rewrites. Our own /api routes (hire-us, oauth/coinpay,
+// webhooks) are filesystem routes and match before these afterFiles rewrites.
+const commandboardApiUrl = process.env.COMMANDBOARD_API_URL;
+
+const nextConfig: NextConfig = {
+  async rewrites() {
+    if (!commandboardApiUrl) return [];
+    const base = commandboardApiUrl.replace(/\/$/, "");
+    return {
+      afterFiles: [
+        { source: "/health", destination: `${base}/health` },
+        { source: "/api/:path*", destination: `${base}/api/:path*` }
+      ]
+    };
+  }
+};
+
+export default nextConfig;