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>

turbo.json

@@ -0,0 +1,43 @@
+{
+  "$schema": "https://turbo.build/schema.json",
+  "ui": "tui",
+  "tasks": {
+    "build": {
+      "dependsOn": ["^build"],
+      "outputs": [".cache/tsbuildinfo.json", "dist/**", "build/**"]
+    },
+    "format": {
+      "outputs": [".cache/.prettiercache"],
+      "outputLogs": "new-only"
+    },
+    "lint": {
+      "dependsOn": ["^build"],
+      "outputs": [".cache/.eslintcache"]
+    },
+    "typecheck": {
+      "dependsOn": ["^build"],
+      "outputs": [".cache/tsbuildinfo.json"]
+    },
+    "dev": {
+      "dependsOn": ["^build"],
+      "cache": false,
+      "persistent": true
+    },
+    "clean": {
+      "cache": false
+    },
+    "setup": {
+      "cache": false,
+      "dependsOn": ["@turbostarter/db#db:setup"]
+    },
+    "test": {
+      "outputs": ["coverage.json"]
+    }
+  },
+  "globalEnv": ["DATABASE_URL", "PRODUCT_NAME", "URL", "DEFAULT_LOCALE"],
+  "globalPassThroughEnv": [
+    "NODE_ENV",
+    "SKIP_ENV_VALIDATION",
+    "npm_lifecycle_event"
+  ]
+}