Widget tests for badge, card and color_picker

#373 in iced-rs/iced_aw — merged 2025-12-24

# unit tests
cargo test --lib widget::badge
cargo test --lib widget::card
cargo test --lib widget::color_picker

# integration tests
cargo test --test badge_integration_tests
cargo test --test card_integration_tests
cargo test --test color_picker_integration_tests