Restructure the theme architecture so 'light', 'dark', and 'system' are
builtin themes with build-time colors (customizable by self-hosters),
while 'black', 'pink', and future themes become presets that apply to a
single 'custom' theme slot.
Key changes:
- Theme type is now 'light' | 'dark' | 'system' | 'custom'
- builtinThemes (light/dark) and themePresets (black/pink/etc.) are
separate maps in themes.ts
- AppConfig gains optional customTheme (ThemeTokens) field
- useTheme exposes applyCustomTheme(tokens) for applying presets
- Custom theme tokens sync across devices via encrypted settings
- Backward compat: legacy 'black'/'pink' values in localStorage and
encrypted settings auto-migrate to custom + preset tokens
- All UI surfaces updated: ThemeSelector, LeftSidebar dropdown,
MobileDrawer cycle, and onboarding ThemeStep
Alex Gleason
7a85ec73ed
