修复图片缩放偏移问题

- 缩放时按比例调整偏移量
- 保持图片中心点不变

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

components/agents/AgentPsdTemplateEditorDialog.tsx

@@ -1302,11 +1302,11 @@ export function AgentPsdTemplateEditorDialog({
                               const newScale = value[0] || 1;
                               updateImagePlacement(selectedImageLayer.id, (current) => {
                                 // 以中心点缩放，调整偏移量保持中心位置不变
-                                const scaleDiff = newScale - current.scale;
+                                const scaleDiff = newScale / current.scale;
                                 return {
                                   scale: newScale,
-                                  offsetX: current.offsetX,
-                                  offsetY: current.offsetY,
+                                  offsetX: current.offsetX * scaleDiff,
+                                  offsetY: current.offsetY * scaleDiff,
                                 };
                               });
                             }}