Fix broken .idea/ pattern and clean up .gitignore

- Fix `./idea` → `.idea/` (typo caused .idea/ directory to not be ignored)
- Remove redundant individual /.idea/* entries (covered by .idea/)
- Remove duplicate .DS_Store entry
- Remove redundant /local.properties (covered by local.properties)
- Reorganize with grouped sections

Author: kirklandsign

.gitignore

@@ -19,20 +19,13 @@ xcuserdata/
 .swiftpm/
 *.xcworkspace/
 *.xcframework/
-*.iml
 
+# Android / IntelliJ
+*.iml
 .gradle
-/local.properties
-./idea
-/.idea/caches
-/.idea/libraries
-/.idea/modules.xml
-/.idea/workspace.xml
-/.idea/navEditor.xml
-/.idea/assetWizardSettings.xml
-.DS_Store
+.idea/
+local.properties
 /captures
 .externalNativeBuild
 .cxx
-local.properties
 *.aar