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>

vitest.config.ts

@@ -0,0 +1,19 @@
+import { defineConfig } from 'vitest/config';
+import react from '@vitejs/plugin-react';
+import { resolve } from 'path';
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'node',
+    include: ['src/**/*.test.ts', 'src/**/*.test.tsx'],
+    exclude: ['tests/golden/**', 'e2e/**'],
+    setupFiles: ['src/test-setup/auth-mock.ts'],
+  },
+  resolve: {
+    alias: {
+      '@': resolve(__dirname, './src'),
+      'server-only': resolve(__dirname, './src/test-setup/server-only-mock.ts'),
+    },
+  },
+});