feat(11-01): replace hex CSS vars with Paperclip OKLCH design tokens

- Replace entire styles.css with OKLCH token system (light + dark modes)
- Switch dark mode from data-theme attribute to .dark CSS class
- Update App.tsx theme toggle to use classList.toggle with system preference detection
- Switch fonts from Inter/JetBrains Mono to Maple Mono/Maple Mono NF CN
- Add chart tokens, sidebar tokens, 0px border radius
- Preserve sidebar-drag, ascii-scroll-track, reduced-motion support
- Remove fontsource font imports from main.tsx

src/renderer/main.tsx

@@ -1,6 +1,3 @@
-import "@fontsource-variable/inter";
-import "@fontsource-variable/jetbrains-mono";
-import "@fontsource/instrument-serif";
 import "./styles.css";
 import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";