feat: add native Svelte UI for robot recording, teleop, and eval

Adds a generic web dashboard at ui/ that works with any robot/teleop
type in lerobot. Calls lerobot-record, lerobot-teleoperate, and
lerobot-eval as background subprocesses.

Features:
- Setup tab: robot type/port/id, dynamic camera configuration
- Record tab: dataset config, teleop device, start/stop recording
- Teleop tab: start/stop teleoperation
- Evaluate tab: policy path, env type, device config
- Live MJPEG camera preview (paused during subprocess, auto-restarts)
- Terminal-style log panel streaming subprocess stdout/stderr
- Hardware discovery: serial ports, CAN interfaces, OpenCV cameras
- Config persistence via localStorage
- Dark theme, responsive camera grid

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/vite.config.js

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vite';
+import { svelte } from '@sveltejs/vite-plugin-svelte';
+
+export default defineConfig({
+  plugins: [svelte()],
+  server: {
+    port: 5173,
+    proxy: {
+      '/api': 'http://localhost:8000',
+    },
+  },
+});