feat(engine): reactive render — animations drive RequestRedraw, focused_mode reactive on Android

All per-frame animation tick systems now write MessageWriter<RequestRedraw>
each frame they have active work, allowing WinitSettings focused_mode to
switch from Continuous to reactive_low_power(100 ms) on Android.

Systems updated:
- advance_card_animations (CardAnimationPlugin)
- advance_card_anims (AnimationPlugin — deal/win cascade)
- tick_shake_anim, tick_settle_anim, tick_foundation_flourish (FeedbackAnimPlugin)
- drive_toast_display (AnimationPlugin — toast countdown)
- drive_auto_complete (AutoCompletePlugin — step interval keepalive)

The 100 ms low-power ceiling means the game timer still ticks ~10×/s
with no input; animations self-sustain via the redraw chain at full
frame rate while active; and the GPU is completely idle between frames
when the board is static.

Each plugin registers add_message::<RequestRedraw>() so the message
type is available under MinimalPlugins in unit tests.

Closes #78, #79

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

solitaire_engine/src/card_animation/mod.rs

@@ -92,6 +92,7 @@ pub use timing::{
 pub use tuning::{AnimationTuning, InputPlatform};
 
 use bevy::prelude::*;
+use bevy::window::RequestRedraw;
 
 use crate::card_plugin::CardEntity;
 use crate::events::{DrawRequestEvent, GameWonEvent, MoveRequestEvent, UndoRequestEvent};
@@ -125,6 +126,7 @@ impl Plugin for CardAnimationPlugin {
             .add_message::<DrawRequestEvent>()
             .add_message::<UndoRequestEvent>()
             .add_message::<GameWonEvent>()
+            .add_message::<RequestRedraw>()
             .init_resource::<DragState>()
             .init_resource::<HoverState>()
             .init_resource::<InputBuffer>()