Dashboard dark mode

[olivrg]

Add a light/dark theme toggle to the dashboard SPA (Tailwind). Persist the choice in React
state for the session.
Good first issue: self-contained frontend task; no backend changes.

[Trinathswain45]

Hi @olivrg , I want to work on this. Pls assign me.

[olivrg]

Thanks @Trinathswain45 it's assigned it to you. A few notes: the toggle should persist in React state for the session (no localStorage. It isn't supported in our setup). Check CONTRIBUTING.md before opening your PR, and feel free to ask here if anything's unclear. Looking forward to it!