fix: enable Chokidar polling for Vite HMR in Docker on Windows

Native fs events do not propagate from Windows hosts into Linux
containers, causing Vite's HMR to stop detecting file changes.

When the DOCKER environment variable is set, Chokidar now falls back
to polling with a 300ms interval, which reliably detects changes
across the Docker volume mount boundary.

Fixes #2456

deployment/docker-compose-local.yaml

@@ -7,6 +7,7 @@ services:
       - VITE_API_HOST=http://localhost:7091
       - VITE_API_STREAMING=$VITE_API_STREAMING
       - VITE_EMBEDDINGS_NAME=$EMBEDDINGS_NAME
+      - DOCKER=true
     ports:
       - "5173:5173"
 

frontend/vite.config.ts

@@ -22,6 +22,12 @@ export default defineConfig(({ mode }) => {
             .map((h) => h.trim())
             .filter(Boolean)
         : [],
+      // Use polling for file watching when running inside Docker.
+      // Native fs events do not propagate from Windows hosts into Linux
+      // containers, so Chokidar falls back to polling which works reliably.
+      watch: env.DOCKER
+        ? { usePolling: true, interval: 300 }
+        : undefined,
     },
     test: {
       environment: 'happy-dom',