Update dependency flutter_lints to v6

pubspec.yaml

@@ -37,7 +37,7 @@ dependencies:
   google_maps_flutter: ^2.12.1
   geolocator: ^14.0.0
   permission_handler: ^12.0.0+1
-  flutter_dotenv: 6.0.0
+  flutter_dotenv: ^5.2.1
   powersync: ^1.12.2
   uuid: ^4.5.1
   supabase_flutter: ^2.8.4
@@ -55,7 +55,7 @@ dev_dependencies:
   # activated in the `analysis_options.yaml` file located at the root of your
   # package. See that file for information about deactivating specific lint
   # rules and activating additional ones.
-  flutter_lints: ^5.0.0
+  flutter_lints: 6.0.0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec