Add disk wear monitoring and fix storage overflow display

- Add disk wear percentage collection from SMART data in backup script
- Add backup_disk_wear_percent metric to backup collector with thresholds
- Display wear percentage in backup widget disk section
- Fix storage section overflow handling to use consistent "X more below" logic
- Update maintenance mode to return pending status instead of unknown

agent/src/collectors/backup.rs

@@ -25,6 +25,25 @@ impl BackupCollector {
     }
 
     async fn read_backup_status(&self) -> Result<Option<BackupStatusToml>, CollectorError> {
+        // Check if we're in maintenance mode
+        if std::fs::metadata("/tmp/cm-maintenance").is_ok() {
+            // Return special maintenance mode status
+            let maintenance_status = BackupStatusToml {
+                backup_name: "maintenance".to_string(),
+                start_time: chrono::Utc::now().format("%Y-%m-%d %H:%M:%S UTC").to_string(),
+                current_time: chrono::Utc::now().format("%Y-%m-%d %H:%M:%S UTC").to_string(),
+                duration_seconds: 0,
+                status: "pending".to_string(),
+                last_updated: chrono::Utc::now().format("%Y-%m-%d %H:%M:%S UTC").to_string(),
+                disk_space: None,
+                disk_product_name: None,
+                disk_serial_number: None,
+                disk_wear_percent: None,
+                services: HashMap::new(),
+            };
+            return Ok(Some(maintenance_status));
+        }
+
         // Check if backup status file exists
         if !std::path::Path::new(&self.backup_status_file).exists() {
             return Ok(None); // File doesn't exist, but this is not an error
@@ -79,7 +98,9 @@ impl BackupCollector {
                 }
             }
             "failed" => Status::Critical,
+            "warning" => Status::Warning, // Backup completed with warnings
             "running" => Status::Ok, // Currently running is OK
+            "pending" => Status::Pending, // Maintenance mode or backup starting
             _ => Status::Unknown,
         }
     }
@@ -379,6 +400,25 @@ impl Collector for BackupCollector {
             });
         }
 
+        if let Some(wear_percent) = backup_status.disk_wear_percent {
+            let wear_status = if wear_percent >= 90.0 {
+                Status::Critical
+            } else if wear_percent >= 75.0 {
+                Status::Warning
+            } else {
+                Status::Ok
+            };
+            
+            metrics.push(Metric {
+                name: "backup_disk_wear_percent".to_string(),
+                value: MetricValue::Float(wear_percent),
+                status: wear_status,
+                timestamp,
+                description: Some("Backup disk wear percentage from SMART data".to_string()),
+                unit: Some("percent".to_string()),
+            });
+        }
+
         // Count services by status
         let mut status_counts = HashMap::new();
         for service in backup_status.services.values() {
@@ -412,6 +452,7 @@ pub struct BackupStatusToml {
     pub disk_space: Option<DiskSpace>,
     pub disk_product_name: Option<String>,
     pub disk_serial_number: Option<String>,
+    pub disk_wear_percent: Option<f32>,
     pub services: HashMap<String, ServiceStatus>,
 }