fix(ci): include pubspec.lock in Dagger source filter

Without pubspec.lock, flutter pub get in the Dagger container resolves
package versions independently of the local lockfile. This caused
flutter_lints to be unresolvable in the container, making dart format
fall back to a different formatter style and flag 90 files as changed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ci/main.go

@@ -19,6 +19,7 @@ func (m *Ci) Base(source *dagger.Directory) *dagger.Container {
 			"assets/",
 			"scripts/",
 			"pubspec.yaml",
+			"pubspec.lock",
 			"analysis_options.yaml",
 			"linux/",
 			"android/",