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>

playwright.config.ts

@@ -0,0 +1,22 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './e2e',
+  fullyParallel: true,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 2 : 0,
+  workers: process.env.CI ? 1 : undefined,
+  reporter: 'list',
+  use: {
+    baseURL: 'http://localhost:3000',
+    trace: 'on-first-retry',
+  },
+  projects: [
+    { name: 'chromium', use: { ...devices['Desktop Chrome'] } },
+  ],
+  webServer: {
+    command: 'pnpm dev',
+    url: 'http://localhost:3000',
+    reuseExistingServer: !process.env.CI,
+  },
+});