chore: update .gitignore patterns

Author: LeanBitLab

.gitignore

@@ -1,37 +1,2 @@
-*.iml
-.idea
-.gradle
-.kotlin
-local.properties
-.DS_Store
-Gemfile
-build
-app/build
-app/release
-app/.cxx
-app/.attach_*
-fastlane/Appfile
-tools/*.txt
-
-# Keys & Secrets (per build-checklist.md)
-*.jks
-*.keystore
-keystore.properties
-signing.properties
-
-# Build logs
-*.log
-
-# Offline model files
-tokenizer.json
-node_modules
-
-# Private Docs
-Pdoc/
-
-# Gemini System Prompts
-GEMINI.md
-
-.antigravityignore
-.gemini/
-.aider*
+# Ignore all files in the app/src/main/java directory
+.aiderignore