refactor: separate standalone and managed room configs

- veins → shunts rename
- add cfg/standalone/ and cfg/<room>/ structure
- remove old data/*.json (moved to cfg/<room>/data/)
- update build.py and ctrl scripts

cfg/standalone/data/rooms.json

@@ -0,0 +1,5 @@
+{
+  "items": [
+    {"name": "pawprint-local", "slug": "pawprint-local", "title": "Pawprint Local", "status": "dev", "config_path": "deploy/pawprint-local"}
+  ]
+}