chore: gitignore the whole .idea/ directory

Untrack IDE-generated .idea/ files that a Gradle sync added; ignore the directory
entirely to keep machine-specific config out of the repo.

.gitignore

@@ -16,12 +16,5 @@
 # Local config / secrets
 local.properties
 
-# IDE
-/.idea/caches
-/.idea/libraries
-/.idea/modules.xml
-/.idea/workspace.xml
-/.idea/navEditor.xml
-/.idea/assetWizardSettings.xml
-/.idea/deploymentTargetSelector.xml
-/.idea/deploymentTargetDropDown.xml
+# IDE (JetBrains / Android Studio) — fully ignored to avoid machine-specific churn
+/.idea/