接入预览画布加减快捷缩放

复用工具栏中心缩放逻辑并统一加减倍率常量
为预览画布增加悬停与键盘焦点作用域
保留既有适配画布和实际尺寸快捷键行为

packages/image-canvas-react/src/ZoomControls.tsx

@@ -1,4 +1,6 @@
 import {
+  CANVAS_ZOOM_IN_FACTOR,
+  CANVAS_ZOOM_OUT_FACTOR,
   canvasDisplayScaleToViewportScale,
   type CanvasViewport,
   formatCanvasDisplayScalePercent,
@@ -27,8 +29,8 @@ export function ZoomControls({
   const actions: CanvasZoomActions = {
     displayPercent: formatCanvasDisplayScalePercent(viewport.scale),
     fit: onFit,
-    zoomIn: () => onScaleFromCenter(viewport.scale * 1.16),
-    zoomOut: () => onScaleFromCenter(viewport.scale * 0.86),
+    zoomIn: () => onScaleFromCenter(viewport.scale * CANVAS_ZOOM_IN_FACTOR),
+    zoomOut: () => onScaleFromCenter(viewport.scale * CANVAS_ZOOM_OUT_FACTOR),
     zoomToDisplayScale: (displayScale) =>
       onScaleFromCenter(canvasDisplayScaleToViewportScale(displayScale)),
   };