Optimize Docker build with multi-stage frontend compilation

• Add frontend build stage to Dockerfile
• Remove --production flag from bun install
• Fix frontend asset integration

.github/workflows/pypi-publish.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Build Frontend WebUI
         run: |
           cd lightrag_webui
-          bun install --frozen-lockfile --production
+          bun install --frozen-lockfile
           bun run build
           cd ..