Convert app into @modernsk/ui component library package

- Add library entry (src/index.ts) re-exporting all components, theme,
  and TooltipProvider
- Add shippable stylesheet (src/styles/index.css): tokens + components
  only, font inlined as base64 at build time
- Build with tsup (ESM + CJS + .d.ts) and esbuild for CSS
- package.json: exports map, files, sideEffects, peerDependencies
  (react/react-dom), correct deps (radix-ui), prepare-on-install
- Fix phantom dependency: declare radix-ui, drop unused @radix-ui/themes
- Remove Storybook boilerplate, Tailwind/PostCSS (unused)
- Keep App.tsx + Rsbuild as dev-only playground (not published)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/assets/logo-mark.svg

@@ -0,0 +1,22 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="128" height="128" viewBox="0 0 128 128" fill="none">
+  <defs>
+    <linearGradient id="tile" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0" stop-color="#d4ff7a"></stop>
+      <stop offset="0.58" stop-color="#bef264"></stop>
+      <stop offset="1" stop-color="#a8e04a"></stop>
+    </linearGradient>
+    <linearGradient id="sheet" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0" stop-color="#22340a"></stop>
+      <stop offset="1" stop-color="#162406"></stop>
+    </linearGradient>
+  </defs>
+  
+  <rect x="6" y="6" width="116" height="116" rx="28" fill="url(#tile)"></rect>
+  <rect x="6" y="6" width="116" height="116" rx="28" fill="none" stroke="#a8e04a" stroke-width="1.5"></rect>
+  <rect x="6.75" y="6.75" width="114.5" height="114.5" rx="27.5" fill="none" stroke="#ffffff" stroke-opacity="0.55" stroke-width="1.5"></rect>
+  
+  <rect x="34" y="40" width="60" height="20" rx="7" fill="url(#sheet)" opacity="0.32"></rect>
+  <rect x="34" y="54" width="60" height="20" rx="7" fill="url(#sheet)" opacity="0.6"></rect>
+  <rect x="34" y="68" width="60" height="24" rx="8" fill="url(#sheet)"></rect>
+  <circle cx="46" cy="80" r="3.4" fill="#bef264"></circle>
+</svg>