feat(ui): create @multica/ui package skeleton

Shared UI package for web, electron, and mobile. Uses subpath exports
following the official shadcn monorepo template pattern.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/ui/components.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://ui.shadcn.com/schema.json",
+  "style": "base-nova",
+  "rsc": true,
+  "tsx": true,
+  "tailwind": {
+    "config": "",
+    "css": "src/styles/globals.css",
+    "baseColor": "zinc",
+    "cssVariables": true
+  },
+  "iconLibrary": "hugeicons",
+  "aliases": {
+    "components": "@multica/ui/components",
+    "utils": "@multica/ui/lib/utils",
+    "hooks": "@multica/ui/hooks",
+    "lib": "@multica/ui/lib",
+    "ui": "@multica/ui/components"
+  }
+}

packages/ui/package.json

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+{
+  "name": "@multica/ui",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "exports": {
+    "./globals.css": "./src/styles/globals.css",
+    "./postcss.config": "./postcss.config.mjs",
+    "./lib/*": "./src/lib/*.ts",
+    "./components/*": "./src/components/*.tsx",
+    "./hooks/*": "./src/hooks/*.ts"
+  },
+  "dependencies": {
+    "@base-ui/react": "^1.1.0",
+    "@hugeicons/core-free-icons": "^3.1.1",
+    "@hugeicons/react": "^1.1.4",
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "shadcn": "^3.7.0",
+    "tailwind-merge": "^3.4.0",
+    "tailwindcss": "^4",
+    "tw-animate-css": "^1.4.0"
+  },
+  "devDependencies": {
+    "@tailwindcss/postcss": "^4",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "typescript": "^5"
+  }
+}

packages/ui/postcss.config.mjs

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+/** @type {import('postcss-load-config').Config} */
+const config = {
+    plugins: { "@tailwindcss/postcss": {} },
+};
+
+export default config;

packages/ui/src/index.ts

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+// This package uses subpath exports.
+// Import like: @multica/ui/lib/utils, @multica/ui/components/button

packages/ui/tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "jsx": "react-jsx",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true,
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["./src/*"],
+      "@multica/ui/*": ["./src/*"]
+    }
+  },
+  "include": ["src"]
+}