chore: initial DSMMG v0.2 — refonte architecturale complète

Mise en place du Design System ManageMate Group v0.2 — refonte du
système de tokens (préfixe --mmg-color-*), 9 presets accent
user-themable validés WCAG AA, overlays Radix UI + Floating UI,
Storybook 8 + Vitest + axe-core en CI, doc Astro Starlight,
DESIGN.md (format google-labs-code) et exports tokens DTCG/CSS/
TS/Figma/Tailwind v3 et v4.

- 4 packages monorepo pnpm : @managemate/{tokens,css,react,icons}
- 62 composants React headless-first (Sheet, HoverCard, ContextMenu,
  Slider, ToggleGroup, AvatarGroup, UserCard, ProfileHeader,
  MetricCard, PricingCard, FeatureCard, Text/Display/Eyebrow/Lead…)
- Lint contraste WCAG : 37/37 paires AA, branché CI
- Toast pile Sonner-style avec ResizeObserver
- Theming user (9 presets) sans casser sémantique fixe
- Identité Synapse (rose #D12B6A) préservée

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

storybook/.storybook/main.ts

@@ -0,0 +1,27 @@
+import type { StorybookConfig } from "@storybook/react-vite";
+
+const config: StorybookConfig = {
+  stories: ["../stories/**/*.mdx", "../stories/**/*.stories.@(js|jsx|mjs|ts|tsx)"],
+  addons: [
+    "@storybook/addon-essentials",
+    "@storybook/addon-interactions",
+    "@storybook/addon-a11y",
+  ],
+  framework: {
+    name: "@storybook/react-vite",
+    options: {},
+  },
+  docs: {
+    autodocs: "tag",
+  },
+  typescript: {
+    reactDocgen: "react-docgen-typescript",
+    reactDocgenTypescriptOptions: {
+      shouldExtractLiteralValuesFromEnum: true,
+      propFilter: (prop) =>
+        prop.parent ? !/node_modules/.test(prop.parent.fileName) : true,
+    },
+  },
+  staticDirs: ["../public"],
+};
+export default config;