Add min_still_distance_gate to LD2410

**Describe the problem you have/What new integration you would like**

When using the LD2410 we can set `max_still_distance_gate` but no `min_still_distance_gate`

**Please describe your use case for this integration and alternatives you've tried:**
Using engineering mode and completely ignoring the presence flags. Which AFAIK is not recommended and not so easy to do.

**Additional context**

I am using the LD2410C in my laundry room, when the wash machine is running the `g2` gate for still energy goes to 100% which starts my lights automation. I do not need detection from gates `0` to `g2` so I just set them to 100% which works until the wash machine runs.

Start by locating the ESPHome LD2410 integration and the existing max_still_distance_gate setting. Trace how that option is configured and applied, then check whether related tests or documentation exist. Done means the integration accepts and applies a corresponding minimum still-distance gate without disrupting the existing maximum setting.

Written by the indexing model from the issue text.