feat: initial commit — Curio mastery tutor

Full Next.js App Router application with:
- AI-graded lesson checkpoints (BKT/Elo mastery tracking)
- Auth.js v5: credentials, Google, GitHub, generic OIDC
- Anonymous-session-first with migrate-on-signin
- Admin panel: users, blueprints, reports, site settings
- Password reset + email verification (nodemailer/SMTP)
- Site config: require_auth + signups_enabled flags
- server-only guards on all DB/generation/verification modules
- PostgreSQL 16 + pgvector, Redis cache, Drizzle ORM
- 271 unit tests (Vitest), golden-eval harness, Playwright e2e stubs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

next-env.d.ts

@@ -0,0 +1,6 @@
+/// <reference types="next" />
+/// <reference types="next/image-types/global" />
+/// <reference path="./.next/types/routes.d.ts" />
+
+// NOTE: This file should not be edited
+// see https://nextjs.org/docs/app/api-reference/config/typescript for more information.