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

prisma.config.ts

@@ -0,0 +1,20 @@
+import 'dotenv/config';
+import { defineConfig, env } from 'prisma/config';
+
+/**
+ * Prisma 7 moved the migration connection URL out of schema.prisma.
+ *
+ * Only the CLI reads this file. The application connects through the pg driver
+ * adapter in src/server/db.ts, which is what lets WP-01 wrap every query in the
+ * tenant-scoping extension required by PLAN.md §3.1.
+ */
+export default defineConfig({
+  schema: 'prisma/schema.prisma',
+  migrations: {
+    path: 'prisma/migrations',
+    seed: 'tsx prisma/seed.ts',
+  },
+  datasource: {
+    url: env('DATABASE_URL'),
+  },
+});