feat: redesign LineSegmentFlow + dev improvements

- LineSegmentFlow: LobeHub brand icons, concave left curves, glow effects
- Dark mode: line colors adapt, animated lines glow in dark theme
- Vite: enable LAN access (host: 0.0.0.0)
- VSCode: workspace settings for performance optimization
- Toast: redesign with icons, progress bar, better animations

frontend/vite.config.ts

@@ -16,7 +16,7 @@ export default defineConfig({
   plugins: [vue(), tailwindcss(), ...(useHttps ? [basicSsl()] : [])],
   server: {
     https: useHttps ? {} : undefined,
-    host: 'localhost', // 确保 host 是 localhost
+    host: '0.0.0.0', // 允许局域网访问
     port: 5173,
     proxy: {
       // 前端 axios baseURL 为 /api，开发时代理到本地 Go 后端，免去跨域与重建