fix(storybook): wire Tailwind v4 theme into Storybook preview

- Split globals.css into globals.css + theme.css so Storybook can
  import design tokens without the @import "tailwindcss" directive
  that breaks Vite's preview module loading
- Prepend @tailwindcss/vite plugin for correct processing order
- Add @source to scan core-ui components for utility class generation

packages/core-ui/package.json

@@ -5,7 +5,8 @@
   "type": "module",
   "exports": {
     ".": "./src/index.ts",
-    "./styles/globals.css": "./src/styles/globals.css"
+    "./styles/globals.css": "./src/styles/globals.css",
+    "./styles/theme.css": "./src/styles/theme.css"
   },
   "scripts": {
     "build": "tsc --noEmit",