Docker image as non-root user

[froozeify]

This PR will closes #213, #234, #225 (probably, waiting for user feedback on it)

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Port 80 Preserved: Using setcap on Apache to allow binding to port 80 without root privileges, avoiding breaking changes for existing deployments as explained in the next section (I'll be inclined to do a dedicated PR with that breaking change).

Process Management:
- Implemented Supervisord to manage services (handling auto restart of them, inspired on Symfony Messenger).
- Replaced system cron with a lightweight PHP worker (cron-worker.sh) managed by Supervisord.

PHP Configuration: Enabled native PHP session garbage collection (session.gc_probability = 1) in glpi.ini since the system cron is no longer available.

Updated startup scripts to check for writable permissions on volume directories instead of attempting to chown them.

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Switching from port 80 to port 8080 (AI beautified)

This is open to debate and should probably be done in a separate PR.

Current Implementation: Port 80 with setcap

How:
We use the Linux capability CAP_NET_BIND_SERVICE to allow the non-root user (www-data) to bind to a privileged port (ports < 1024).

RUN setcap cap_net_bind_service=+ep /usr/sbin/apache2

Pros:

• No Breaking Changes: Existing deployments using docker-compose.yml or docker run -p 80:80 continue to work without modification.
• User Experience: Users don't need to change their habits or configurations.

Cons:

• Dependencies: Requires installing libcap2-bin.
• Security: Technically grants a small capability to the binary, though widely considered safe and standard practice for web servers.

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Alternative Considered: Port 8080 (High Ports)

Proposal: Change standard Apache listener to Port 8080.

How:
Configure Apache to Listen on 8080 instead of 80.

Pros:

• Pure Non-Root: No special Linux capabilities (setcap) required. The process is completely unprivileged standard application.
• Simplicity: No need to install libcap2-bin.

Cons:

• Breaking Change: This is a major breaking change for all existing users.
  • Current docker-compose.yml:

    ports:
      - "80:80"  # BROKEN: Container no longer listens on 80

  • Required change:

    ports:
      - "80:8080" # FIXED: Map host 80 to container 8080