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

dashboard/src/ui/widgets/backup.rs

@@ -30,6 +30,8 @@ pub struct BackupWidget {
     backup_disk_product_name: Option<String>,
     /// Backup disk serial number from SMART data
     backup_disk_serial_number: Option<String>,
+    /// Backup disk wear percentage from SMART data
+    backup_disk_wear_percent: Option<f32>,
     /// Backup disk filesystem label
     backup_disk_filesystem_label: Option<String>,
     /// Number of completed services
@@ -65,6 +67,7 @@ impl BackupWidget {
             backup_disk_used_gb: None,
             backup_disk_product_name: None,
             backup_disk_serial_number: None,
+            backup_disk_wear_percent: None,
             backup_disk_filesystem_label: None,
             services_completed_count: None,
             services_failed_count: None,
@@ -197,6 +200,9 @@ impl Widget for BackupWidget {
                 "backup_disk_serial_number" => {
                     self.backup_disk_serial_number = Some(metric.value.as_string());
                 }
+                "backup_disk_wear_percent" => {
+                    self.backup_disk_wear_percent = metric.value.as_f32();
+                }
                 "backup_disk_filesystem_label" => {
                     self.backup_disk_filesystem_label = Some(metric.value.as_string());
                 }
@@ -328,21 +334,31 @@ impl BackupWidget {
             );
             lines.push(ratatui::text::Line::from(disk_spans));
 
-            // Serial number as sub-item
+            // Collect sub-items to determine tree structure
+            let mut sub_items = Vec::new();
+            
             if let Some(serial) = &self.backup_disk_serial_number {
-                lines.push(ratatui::text::Line::from(vec![
-                    ratatui::text::Span::styled("  ├─ ", Typography::tree()),
-                    ratatui::text::Span::styled(format!("S/N: {}", serial), Typography::secondary())
-                ]));
+                sub_items.push(format!("S/N: {}", serial));
             }
-
-            // Usage as sub-item
+            
+            if let Some(wear) = self.backup_disk_wear_percent {
+                sub_items.push(format!("Wear: {:.0}%", wear));
+            }
+            
             if let (Some(used), Some(total)) = (self.backup_disk_used_gb, self.backup_disk_total_gb) {
                 let used_str = Self::format_size_with_proper_units(used);
                 let total_str = Self::format_size_with_proper_units(total);
+                sub_items.push(format!("Usage: {}/{}", used_str, total_str));
+            }
+            
+            // Render sub-items with proper tree structure
+            let num_items = sub_items.len();
+            for (i, item) in sub_items.into_iter().enumerate() {
+                let is_last = i == num_items - 1;
+                let tree_char = if is_last { "  └─ " } else { "  ├─ " };
                 lines.push(ratatui::text::Line::from(vec![
-                    ratatui::text::Span::styled("  └─ ", Typography::tree()),
-                    ratatui::text::Span::styled(format!("Usage: {}/{}", used_str, total_str), Typography::secondary())
+                    ratatui::text::Span::styled(tree_char, Typography::tree()),
+                    ratatui::text::Span::styled(item, Typography::secondary())
                 ]));
             }
         }