Add archive count to backup disk display

agent/src/collectors/backup.rs

@@ -142,6 +142,11 @@ impl BackupCollector {
                     // Build service list for this disk
                     let services: Vec<String> = backup_status.services.keys().cloned().collect();
 
+                    // Calculate total archives across all services on this disk
+                    let total_archives: i64 = backup_status.services.values()
+                        .map(|service| service.archive_count)
+                        .sum();
+
                     // Create disk data
                     let disk_data = BackupDiskData {
                         serial: backup_status.disk_serial_number.unwrap_or_else(|| "Unknown".to_string()),
@@ -155,6 +160,7 @@ impl BackupCollector {
                         disk_total_gb: total_gb,
                         usage_status,
                         services,
+                        total_archives,
                     };
 
                     disks.push(disk_data);