🔧 fix: use named volume for backups in coolify deployment

[thies2005]

🎯 What
Replaced relative local bind mounts (./backups) with a Docker named volume (backups) in Web/docker-compose.coolify.yml.

💡 Why
When deploying via Coolify, the deployment process clones the repository into an ephemeral directory. Using relative path bind mounts like ./backups can cause deployment failures, lack of persistence, or permission errors. Coolify explicitly supports and expects standard Docker named volumes (e.g., backups) which it provisions and manages independently of the repository source directory.

✅ Verification
Ran docker compose -f Web/docker-compose.coolify.yml config locally to verify that the compose file is still syntactically correct and properly parses the named volumes instead of bind mounts.

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PR created automatically by Jules for task 5392145412997513934 started by @thies2005

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