feat: add Vite dev server proxy configuration for local development

Enable concurrent web development workflow with Vite HMR instead of requiring pre-build. Configure Vite server to listen on 0.0.0.0 for LAN access, proxy /api and /socket.io to backend (127.0.0.1:3006), and run dev:server and dev:web together.

package.json

@@ -3,6 +3,7 @@
     "private": true,
     "workspaces": ["cli", "server", "web"],
     "scripts": {
+        "dev": "concurrently \"bun run dev:server\" \"bun run dev:web\" --kill-others-on-exit",
         "build": "bun run build:cli && bun run build:server && bun run build:web",
         "build:cli": "cd cli && bun run build",
         "build:server": "cd server && bun run build",
@@ -16,6 +17,7 @@
         "test": "cd cli && bun run test"
     },
     "devDependencies": {
+        "concurrently": "^9.2.1",
         "vite-plugin-pwa": "^1.2.0",
         "workbox-window": "^7.4.0"
     }