Fix firewalld reload in Docker deployment

[erfansahaf]

Summary

This PR fixes the firewalld reload functionality when running the application inside a Docker container.

Problem

The original implementation tried to call firewall-cmd --reload inside the Docker container, but:

1. The container didn't have access to the firewalld socket (/var/run/firewalld/)
2. The firewall-cmd client wasn't installed in the container
3. This caused silent failures and the rules weren't being reloaded

Solution

1. Install firewalld client in Dockerfile - Added apt-get install -y firewalld to install the firewalld client (not the daemon) inside the container
2. Mount firewalld socket - Added /var/run/firewalld:/var/run/firewalld volume mount in docker-compose.yml to expose the host's firewalld socket to the container
3. Run as root - Added USER root in Dockerfile to ensure proper permissions to access the socket
4. Improved error handling - Enhanced the /reload endpoint to return proper JSON responses with helpful error messages

How it works

When running in Docker:

• The container has firewall-cmd installed (client only)
• The firewalld socket from the host is mounted into the container
• When /reload is called, it uses the mounted socket to communicate with the host's firewalld daemon over DBus
• The host's firewalld is signaled to reload its rules

Testing

The changes have been made locally. To test:

1. Ensure firewalld is running on the host machine
2. Build and run the container with docker compose up --build
3. Make changes to firewall rules through the GUI
4. Click the reload button - it should now successfully reload firewalld