Enable lockFileMaintenance in Renovate config

Adds weekly transitive dependency refresh for both npm and uv lockfiles.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

renovate.json

@@ -1,3 +1,6 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "lockFileMaintenance": {
+    "enabled": true
+  }
 }