feat: turbostarter boilerplate

Production-ready Next.js boilerplate with:
- Runtime env validation (fail-fast on missing vars)
- Feature-gated config (S3, Stripe, email, OAuth)
- Docker + Coolify deployment pipeline
- PostgreSQL + pgvector, MinIO S3, Better Auth
- TypeScript strict mode (no ignoreBuildErrors)
- i18n (en/es), AI modules, billing, monitoring

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.vscode/extensions.json

@@ -0,0 +1,9 @@
+{
+  "recommendations": [
+    "dbaeumer.vscode-eslint",
+    "expo.vscode-expo-tools",
+    "esbenp.prettier-vscode",
+    "yoavbls.pretty-ts-errors",
+    "bradlc.vscode-tailwindcss"
+  ]
+}