chore(gitignore): ajout secrets Android/iOS + Flutter dev tools

Ajouts critiques pour éviter les fuites de secrets :
- Android signing : key.properties, *.jks, *.keystore, google-services.json
  (local.properties déjà ignoré via android/.gitignore)
- iOS : xcuserdata/, Pods/, GoogleService-Info.plist, Flutter/Generated.xcconfig
- Flutter Version Management : .fvm/
- DevTools : devtools_options.yaml
- Build multi-plateforme : windows/linux/macos flutter ephemeral
- Obfuscation maps + symbols
- Dumps / crashes : *.stackdump, hs_err_pid*
- OS artefacts : .DS_Store, Thumbs.db, desktop.ini

.gitignore

@@ -66,3 +66,65 @@ test/.test_coverage.dart
 # Local scripts
 *.local.sh
 *.local.bat
+
+# ============================================
+# Android signing / secrets — NE JAMAIS COMMIT
+# ============================================
+android/key.properties
+android/app/key.properties
+android/app/upload-keystore.jks
+**/*.jks
+**/*.keystore
+android/app/google-services.json
+android/app/src/*/google-services.json
+
+# local.properties contient le chemin SDK local et dev.host (IP LAN)
+android/local.properties
+android/app/local.properties
+
+# Gradle cache / NDK
+.gradle/
+**/android/.gradle/
+**/android/app/.cxx/
+**/android/captures/
+
+# ============================================
+# iOS — Xcode user data + signing
+# ============================================
+**/ios/Runner.xcworkspace/xcuserdata/
+**/ios/Runner.xcodeproj/xcuserdata/
+**/ios/Runner.xcodeproj/project.xcworkspace/xcuserdata/
+**/ios/Pods/
+**/ios/Podfile.lock.orig
+**/ios/.symlinks/
+**/ios/Flutter/Generated.xcconfig
+**/ios/Flutter/App.framework
+**/ios/Flutter/Flutter.framework
+**/ios/Flutter/Flutter.podspec
+**/ios/Runner/GoogleService-Info.plist
+**/ios/ServiceDefinitions.json
+
+# ============================================
+# Flutter outils dev
+# ============================================
+.fvm/
+devtools_options.yaml
+flutter_export_environment.sh
+
+# Build outputs multi-plateformes
+/windows/flutter/ephemeral/
+/macos/Flutter/ephemeral/
+/linux/flutter/ephemeral/
+
+# Profiling
+*.obfuscation_map.json
+*.symbols
+
+# Dumps / crashes
+*.stackdump
+hs_err_pid*
+
+# Temp OS
+.DS_Store
+Thumbs.db
+desktop.ini