🐛 [BUG] 仪表盘(渐变色) 颜色过度问题

当数值较小时，发现颜色从左往右过度的，应该从下往上过度才对。


Start by reproducing the dashboard gradient issue with a small value and inspect the dashboard chart implementation to find where the gradient direction is set. Compare the rendered direction with the attached image; done means the gradient runs from bottom to top for small values rather than from left to right.

Written by the indexing model from the issue text.