admin theme manager

resources/tmp/themes/custom/meta/manifest.json

@@ -1,10 +1,12 @@
 {
   "name": "Custom",
   "version": "0.1",
+  "slug": "custom",
   "description": "Custom admin theme",
-  "preview": "preview.png",
+  "preview": "nrnv2024_640x360.jpg",
   "resource": "/resources/custom",
   "resource_path": "{RESOURCES}/custom",
   "layout": "main.php",
-  "layout_path": "{APP}/admin_themes/custom/layout"
-}
+  "theme_path": "{APP}/admin_themes/{slug}",
+  "layout_path": "{APP}/admin_themes/{slug}/layout"
+}