feat(lib): add require_disk_space helper and enforce pre-flight disk checks

- add `require_disk_space` function to lib/common.sh with dedup logic for shared filesystems
- gate cloudpanel, coolify, pterodactyl installs behind a 2–3 GB disk check
- gate uptime-kuma, proxmox update, harden, update-server, and server-benchmark behind 300–1024 MB disk checks
- fail early with a clear error before apt installs or config writes can leave the system in a partial state

apps/proxmox.sh

@@ -242,16 +242,18 @@ clear_cache() {
 
 update_proxmox() {
     echo -e "${WHITE}${BOLD}UPDATE PROXMOX VE${NC}\n"
-    
+
     check_proxmox || return 1
-    
+
+    require_disk_space 1024 || return 1
+
     # Configure non-interactive mode
     export DEBIAN_FRONTEND=noninteractive
     export NEEDRESTART_MODE=a
     export NEEDRESTART_SUSPEND=1
-    
+
     local start_time=$(date +%s)
-    
+
     run_spinner "Updating package lists..." "apt update"
     
     echo ""