fix(engine): foundation→tableau drag hints, z-lift, and Android battery drain

Fixes #34, #35, #36

- all_hints: add Foundation as source for Tableau hints (guarded by
  take_from_foundation); previously H key never suggested Foundation→Tableau
- end_drag / touch_end_drag: enforce take_from_foundation at input layer
  so a rejected-by-core MoveRequestEvent is never fired
- animation_plugin: pub CARD_ANIM_Z_LIFT so card_plugin can consume it
- update_card_entity: set CardAnim start.z = z + CARD_ANIM_Z_LIFT to
  eliminate 1-frame z artifact where animated card appeared behind resting cards
- solitaire_app: use AutoVsync on Android (caps GPU at display Hz vs
  spinning at 200+ fps); add WinitSettings unfocused reactive_low_power
  so app draws ~1fps when backgrounded

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

solitaire_engine/src/card_plugin.rs

@@ -23,7 +23,7 @@ use solitaire_core::pile::PileType;
 
 use solitaire_core::rules::{can_place_on_foundation, can_place_on_tableau};
 
-use crate::animation_plugin::{CardAnim, EffectiveSlideDuration};
+use crate::animation_plugin::{CardAnim, EffectiveSlideDuration, CARD_ANIM_Z_LIFT};
 use crate::card_animation::CardAnimation;
 use crate::events::{CardFaceRevealedEvent, CardFlippedEvent, StateChangedEvent};
 use crate::game_plugin::GameMutation;
@@ -963,7 +963,12 @@ fn update_card_entity(
     if !has_card_animation {
         // Slide to the new position when it differs meaningfully; snap otherwise.
         if (cur.truncate() - target.truncate()).length() > 1.0 && slide_secs > 0.0 {
-            let start = Vec3::new(cur.x, cur.y, z); // update Z immediately
+            // Lift the card immediately on the first frame of the animation so
+            // it never appears behind a card that is already resting at the
+            // destination slot. `advance_card_anims` will maintain this lift
+            // throughout the tween and snap to `target` (without lift) on
+            // completion.
+            let start = Vec3::new(cur.x, cur.y, z + CARD_ANIM_Z_LIFT);
             commands
                 .entity(entity)
                 .insert(Transform::from_translation(start))