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/depots.json

@@ -0,0 +1,12 @@
+{
+  "items": [
+    {
+      "name": "feature-form",
+      "slug": "feature-form",
+      "title": "Feature Forms",
+      "status": "ready",
+      "source_template": "feature-form",
+      "data_path": "album/book/feature-form-samples/feature-form"
+    }
+  ]
+}