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>

tsconfig.json

@@ -0,0 +1,23 @@
+{
+  "compilerOptions": {
+    "ignoreDeprecations": "6.0",
+    "lib": ["DOM", "ES2020"],
+    "jsx": "react-jsx",
+    "target": "ES2020",
+    "noEmit": true,
+    "skipLibCheck": true,
+    "useDefineForClassFields": true,
+
+    /* modules */
+    "moduleDetection": "force",
+    "moduleResolution": "bundler",
+    "verbatimModuleSyntax": true,
+    "resolveJsonModule": true,
+    "allowImportingTsExtensions": true,
+
+    /* type checking */
+    "noUnusedLocals": true,
+    "noUnusedParameters": true
+  },
+  "include": ["src"]
+}