[Question] DotIndicator always on

**Is your feature request relasted to a problem? Please describe.**
Hi guys, I have two questions:
- Is it possible to create the chart with the indicator dot always selected (even if its not pressed)?
- Is it possible to create a gradient in the graph line and change it with the user interaction?

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**

No file or test is named. Start by reviewing FL Chart's line-chart dot indicator behavior and line-gradient support, then clarify whether both requested interactions belong in this issue. Done should be defined as explicit acceptance criteria for the persistent indicator and interaction-dependent gradient, along with a relevant test or example.

Written by the indexing model from the issue text.