- Inline <script> in app.html applies saved localStorage theme before first
paint to prevent flash of wrong theme
- ThemeToggle.svelte: moon/sun button, localStorage persistence, sets
data-theme on <html>, defaults to system preference on first visit
- Placed in +layout.svelte between language selector and user menu
- E2E tests cover visibility, toggle, reverse toggle, persistence, and
no-flash behaviour — all 6 passing
Refs #64
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
