feat: eliminate theme flash on initial paint (FOUC) via inline script [FaaFyfxR9WAQrL7FcAgEHJvztd8cVMxvjHRS55rw1nwH] - #520
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Closes #389
Problem
ThemeProviderinitialisesuseState<Theme>('dark')on the server. The client then reads localStorage/matchMedia insideuseEffect. First paint is always dark, then snaps to the correct theme on hydration — causing a flash of incorrect theme (FOUC).Changes
New
initializeTheme()export incomponents/ThemeProvider.tsx— a standalone function that reads the saved theme from localStorage (or falls back toprefers-color-scheme/"dark") and applies it todocument.documentElement.Inline script in
app/layout.tsx— a synchronous IIFE injected into the HTML<head>that runs before React hydrates. It reads the theme and sets thedarkclass +colorSchemestyle on<html>immediately, so the first paint always has the correct theme.Acceptance Criteria
prefers-color-schemeis respected as fallbacksuppressHydrationWarningalready present on<html>