Add the design system extracted from the app

design/ holds the tokens for all six themes, the type scale, spacing,
radii and sizes, the brand and usage guidelines, a guide and static
preview for each component, the logo and icons as SVG, and wireframes of
the tablet and foldable column layout.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RhmDdrN5hgWrgRcFLAMsV6

design/components/SettingToggle/README.md

@@ -0,0 +1,8 @@
+# SettingToggle
+
+A setting with a one-line explanation and a Material Switch.
+
+- **Consumer provides:** a title, a note and the checked state.
+- Title in `body-large` / `on-surface`; the note under it in `body-small` / `on-surface-variant`; the Switch at the end. `space-12` above each toggle.
+- The note says what the setting does *and* when it applies ("Applies to the dark themes; saves power on OLED screens"). Put a toggle beside the choice it modifies — OLED sits right under the theme chips.
+- Switch on: `primary` track, `on-primary` thumb. Off: `surface-container-highest` track with an `outline` border and thumb.