feat(ui): 登录滑出面板高度降低40%（85vh→51vh）

cfc-frontend/components/login-sheet.vue

@@ -256,8 +256,8 @@ export default {
   left: 0;
   right: 0;
   bottom: 0;
-  height: 85vh;
-  max-height: 85vh;
+  height: 51vh;
+  max-height: 51vh;
   background: linear-gradient(180deg, #fffaf3 0%, #fff3e4 100%);
   border-radius: 24rpx 24rpx 0 0;
   overflow: hidden;