Bump turborepo from 2.8.11 to 2.9.4

Update turbo version in package.json and regenerate lock file.
CI workflow files (.github/workflows/) also need TURBO_VERSION updated
to 2.9.4 but require a token with `workflow` scope to push.

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

Author: lukesandberg

package.json

@@ -301,7 +301,7 @@
     "tree-kill": "1.2.2",
     "tsec": "0.2.1",
     "tsx": "4.19.2",
-    "turbo": "2.8.11",
+    "turbo": "2.9.4",
     "typescript": "5.9.2",
     "typescript-eslint": "8.46.0",
     "unfetch": "4.2.0",