Visualisation: Add dark mode

[sanika-n]

This PR adds the Solara Dark theme to Mesa

By default, the theme is set to match the user's system settings, however, it can be controlled by clicking on the toggle at the right end of the app bar once solara is launched

Dark Mode (Auto for me)

Light Mode

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
BoltzmannWealth	small	🔴 +13.5% [+13.0%, +13.9%]	🔵 +0.8% [+0.7%, +1.0%]
BoltzmannWealth	large	🔵 +20.2% [+1.6%, +56.8%]	🔴 +15.2% [+13.4%, +16.7%]
Schelling	small	🔵 +1.6% [+1.2%, +2.0%]	🔵 +0.5% [+0.3%, +0.6%]
Schelling	large	🔵 +0.4% [+0.1%, +0.7%]	🔵 -0.6% [-1.7%, +0.7%]
WolfSheep	small	🔵 -1.4% [-1.7%, -1.0%]	🔵 -0.2% [-0.5%, +0.1%]
WolfSheep	large	🔵 -0.6% [-1.4%, +0.1%]	🔵 +0.6% [-1.6%, +2.8%]
BoidFlockers	small	🔴 +4.5% [+4.0%, +5.0%]	🔵 +3.2% [+2.5%, +3.6%]
BoidFlockers	large	🔵 +3.3% [+2.9%, +3.8%]	🔵 +2.7% [+2.3%, +3.0%]

[EwoutH]

Easy, nice and uncomplicated. I like it!

I will leave the merge for another maintainer.