feat(core): initialize project skeleton with Electron + React + TypeScript

Set up the complete project foundation for ClawX, a graphical AI assistant:

- Electron main process with IPC handlers, menu, tray, and gateway management
- React renderer with routing, layout components, and page scaffolding
- Zustand state management for gateway, settings, channels, skills, chat, and cron
- shadcn/ui components with Tailwind CSS and CSS variable theming
- Build tooling with Vite, electron-builder, and TypeScript configuration
- Testing setup with Vitest and Playwright
- Development configurations (ESLint, Prettier, gitignore, env example)

postcss.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+};