fix(frontend): 内容分享海报尺寸调整(800→633)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

cfc-frontend/components/ContentSharePoster.vue

@@ -143,7 +143,7 @@ export default {
           var scaleY = 1
           if (rect && rect.width && rect.height) {
             scaleX = rect.width / 500
-            scaleY = rect.height / 800
+            scaleY = rect.height / 633
           }
           self._renderPoster(scaleX, scaleY)
         })
@@ -644,7 +644,7 @@ export default {
       uni.canvasToTempFilePath({
         canvasId: 'contentPosterCanvas',
         destWidth: 500,
-        destHeight: 800,
+        destHeight: 633,
         success: function(res) {
           uni.saveImageToPhotosAlbum({
             filePath: res.tempFilePath,
@@ -699,7 +699,7 @@ export default {
 }
 .poster-canvas {
   width: 620rpx;
-  height: 992rpx;
+  height: 792rpx;
   border-radius: 16rpx;
 }
 .poster-actions {