Add Docker support with runtime environment variable configuration

- Remove temporary arne.js file
- Add runtime configuration via window.__RUNTIME_CONFIG__
- Create public/config.template.js for hostname injection
- Add Dockerfile with multi-stage build (node + nginx)
- Add docker-entrypoint.sh to generate config.js at startup
- Add .dockerignore
- Update all components to use runtime config instead of arne.js
- Update index.html to load config.js before app

This allows deploying the same Docker image to different environments
by setting the API_HOSTNAME environment variable at runtime.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

.dockerignore

@@ -0,0 +1,4 @@
+node_modules
+.git
+dist
+.DS_Store