chore: convert to real pnpm workspace, single root lockfile

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -0,0 +1,13 @@
+{
+  "name": "new_starr",
+  "private": true,
+  "packageManager": "pnpm@11.3.0",
+  "scripts": {
+    "dev": "concurrently -n api,web -c blue,green \"pnpm --filter api dev\" \"pnpm --filter web dev\"",
+    "build": "pnpm --filter web build",
+    "start": "pnpm --filter api start"
+  },
+  "devDependencies": {
+    "concurrently": "^9.2.1"
+  }
+}