WP-00: application foundation

Scaffolds the project: Next.js 16 App Router with strict TypeScript,
Prisma 7 on PostgreSQL 16, Tailwind 4, Vitest, Playwright, CI, and a
standalone Docker image that applies migrations on boot.

Makes the no-tracker rule of PLAN.md 3.7 enforceable rather than
stated. A per-request nonce-based CSP names no external origin, a unit
test fails if any network directive gains one, and a second test fails
if a tracking package appears in package.json. The end-to-end test
drives the standalone server the Docker image runs, not `next dev`,
so a proxy matcher that stopped matching could not pass unnoticed.

Environment is validated at import, so a missing DATABASE_URL fails at
boot with a readable message instead of surfacing later as a driver
error mid-export. ENCRYPTION_KEY is checked to be 32 bytes.

Three deviations from the plan, recorded in PLAN.md and README:
Next 16 rather than 15, `proxy.ts` rather than the now-deprecated
`middleware.ts`, and database-backed sessions rather than Auth.js v5,
which is still beta and whose JWTs would make the session revocation
required by compliance item 23 awkward.

Verified locally against PostgreSQL 16: migrations apply, extensions
created, typecheck, lint, 9 unit tests and the end-to-end header test
all pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cr9dkEHwbDgkWPnyGj1Rjv

next.config.ts

@@ -0,0 +1,35 @@
+import type { NextConfig } from 'next';
+
+const nextConfig: NextConfig = {
+  // Docker image: ship only what the server needs.
+  output: 'standalone',
+  reactStrictMode: true,
+  poweredByHeader: false,
+
+  // Security headers that do not need a per-request nonce.
+  // The Content-Security-Policy is set in src/proxy.ts because it does.
+  async headers() {
+    return [
+      {
+        source: '/:path*',
+        headers: [
+          { key: 'X-Content-Type-Options', value: 'nosniff' },
+          { key: 'X-Frame-Options', value: 'DENY' },
+          { key: 'Referrer-Policy', value: 'no-referrer' },
+          {
+            key: 'Strict-Transport-Security',
+            value: 'max-age=63072000; includeSubDomains; preload',
+          },
+          // No browser feature in this app needs these. Denying them keeps a
+          // future dependency from silently reaching for a camera or a GPS fix.
+          {
+            key: 'Permissions-Policy',
+            value: 'camera=(), microphone=(), geolocation=(), interest-cohort=()',
+          },
+        ],
+      },
+    ];
+  },
+};
+
+export default nextConfig;