refactor: adapt Button fields to the cce-ui Phase 5 migration

Button::new now returns Adapted<Button>; concrete-typed fields become
Adapted<Button>. Construction sites, builder chains, and method calls
are unchanged (Deref + Element forwards + mirrored builders).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01LkfJazPs9bRchkcozmxXCX

 src/main.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 46ca686..2736704 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -367,8 +367,8 @@ enum Message {
 
 struct ColorApp {
     root_window: Backplate,
-    apply_btn: Button,
-    cancel_btn: Button,
+    apply_btn: cce_ui::widget::Adapted<cce_ui::widget::Button>,
+    cancel_btn: cce_ui::widget::Adapted<cce_ui::widget::Button>,
     sliders: Vec<ColorSlider>,
 
     red: f32,