singleton pattern usage cursor rule

Author: Daggerpov

.cursor/rules.json

@@ -111,6 +111,11 @@
       "pattern": "\\.(swift)$",
       "rule": "Always use the APIService methods for network calls. Never implement direct URL session calls in ViewModels"
     },
+    {
+      "name": "Singleton Pattern Usage",
+      "pattern": "\\.(swift)$",
+      "rule": "ALWAYS use AppCache.shared directly instead of creating @ObservedObject or @StateObject properties. Never use '@ObservedObject private var appCache = AppCache.shared' or similar patterns. Access AppCache.shared directly in code. For UserAuthViewModel, use UserAuthViewModel.shared directly as well."
+    },
     {
       "name": "App Color Usage - Universal Colors",
       "pattern": "\\.(swift)$",