Dark mode with persistence (Tailwind)

[unrealbg]

Problem

No dark mode or persisted theme preference; user experience is inconsistent with system theme.

Proposal

• Add theme toggle with preference persisted to localStorage and system detection (prefers-color-scheme).
• Toggle should not cause FOUC (flash of unstyled content).

Alternatives considered

• System theme only, no manual toggle.

Acceptance criteria

• Toggle switches theme without FOUC
• Preference persisted in localStorage
• Respects prefers-color-scheme

Technical notes

• Tailwind dark mode class strategy
• Initialize theme before Blazor boot

Risks

• Theme flickering or incorrect detection.

Additional context

Labels: enhancement, ui, a11y