style: Set correct dark-theme message background color

[loveucifer]

Fixes #1685.

The DesignVariables.bgMessageRegular color was slightly incorrect in dark mode. The previous value, const HSLColor.fromAHSL(1, 0, 0, 0.11).toColor(), resulted in a background color of #1C1C1C, which created a noticeable contrast with the main background. This value might have been a legacy from a previous design iteration.

The Figma design clearly specifies #1D1D1D for the bg-message-regular variable in dark mode. This change updates the value to match the design specification, ensuring a consistent and uniform background for messages.

Before

After

[gnprice]

Thanks. Can you post a pair of screenshots that are as similar as possible except for your change? With the current screenshots it's difficult to tell what's caused by your change, because all the content in the screenshots is different.

Using Flutter's hot reload:
https://docs.flutter.dev/tools/hot-reload
it should be possible to switch quickly back and forth between the "before" and "after" versions of the code, without leaving your place in the running app. That should make it possible to get pretty much the exact same shot in both "before" and "after".

[gnprice]

For the backstory in the description, see the comment I just posted on the issue: #1685 (comment)

[gnprice]

These before/after screenshots would also benefit from going into a table. See Zulip's contributor docs here:
https://zulip.readthedocs.io/en/latest/contributing/reviewable-prs.html#demonstrating-visual-changes

[loveucifer]

thanks , I hope this solve it
before

after

[loveucifer]

I Also had some doubts on the assigned tasks , i saw some of them that were labelled beginner friendly were assigned to someone else , so am i not allowed to work on it ?