Hide backup panel when no backup data is present

- Add has_data() method to BackupWidget to check if backup metrics exist
- Modify dashboard layout to conditionally show backup panel only when data exists
- When no backup data: system panel takes full left side height
- When backup data exists: system and backup panels share left side equally

Prevents empty backup panel from taking up screen space unnecessarily.

dashboard/src/ui/mod.rs

@@ -275,21 +275,40 @@ impl TuiApp {
             ])
             .split(main_chunks[1]);
 
-        // Left side: system on top, backup on bottom (equal height)
-        let left_chunks = ratatui::layout::Layout::default()
-            .direction(Direction::Vertical)
-            .constraints([
-                Constraint::Percentage(ThemeLayout::SYSTEM_PANEL_HEIGHT), // System section
-                Constraint::Percentage(ThemeLayout::BACKUP_PANEL_HEIGHT), // Backup section
-            ])
-            .split(content_chunks[0]);
+        // Check if backup panel should be shown
+        let show_backup = if let Some(hostname) = self.current_host.clone() {
+            let host_widgets = self.get_or_create_host_widgets(&hostname);
+            host_widgets.backup_widget.has_data()
+        } else {
+            false
+        };
+
+        // Left side: dynamic layout based on backup data availability
+        let left_chunks = if show_backup {
+            // Show both system and backup panels
+            ratatui::layout::Layout::default()
+                .direction(Direction::Vertical)
+                .constraints([
+                    Constraint::Percentage(ThemeLayout::SYSTEM_PANEL_HEIGHT), // System section
+                    Constraint::Percentage(ThemeLayout::BACKUP_PANEL_HEIGHT), // Backup section
+                ])
+                .split(content_chunks[0])
+        } else {
+            // Show only system panel (full height)
+            ratatui::layout::Layout::default()
+                .direction(Direction::Vertical)
+                .constraints([Constraint::Percentage(100)]) // System section takes full height
+                .split(content_chunks[0])
+        };
 
         // Render title bar
         self.render_btop_title(frame, main_chunks[0], metric_store);
 
         // Render new panel layout
         self.render_system_panel(frame, left_chunks[0], metric_store);
-        self.render_backup_panel(frame, left_chunks[1]);
+        if show_backup && left_chunks.len() > 1 {
+            self.render_backup_panel(frame, left_chunks[1]);
+        }
 
         // Render services widget for current host
         if let Some(hostname) = self.current_host.clone() {