chore: initialize monorepo with Turborepo and pnpm

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

turbo.json

@@ -0,0 +1,24 @@
+{
+  "$schema": "https://turbo.build/schema.json",
+  "globalDependencies": ["**/.env.*local"],
+  "pipeline": {
+    "build": {
+      "dependsOn": ["^build"],
+      "outputs": [".next/**", "!.next/cache/**", "dist/**"]
+    },
+    "dev": {
+      "cache": false,
+      "persistent": true
+    },
+    "lint": {},
+    "type-check": {
+      "dependsOn": ["^build"]
+    },
+    "db:generate": {
+      "cache": false
+    },
+    "db:push": {
+      "cache": false
+    }
+  }
+}