Introduce a breathing pulse effect (red fill + white border) for attack
target tiles to draw the player's eye when in "must pick a target" fire
mode. The previous static tint is preserved for the indirect-range preview
shown while a unit is merely selected.
- showAttackTiles now accepts optional { pulse: true } parameter
- Added tween-based animation with Sine.easeInOut breathing effect
- Properly clean up pulse tween in destroy() and clearOverlays()
- Updated AdvanceWarsGame to pass pulse: true when showing targets
