Fix keyboard navigation and panel scrolling issues

- Remove Network panel from navigation cycle
- Fix system panel scrolling to work in both directions
- Add complete scroll support to Services and Backup panels
- Update panel cycling to System → Services → Backup only
- Enhance scroll indicators with proper bounds checking
- Clean up unused Network panel code and references

Resolves issues with non-functional up/down scrolling and
mystery network panel appearing during navigation.

dashboard/src/ui/widgets/system.rs

@@ -520,9 +520,13 @@ impl SystemWidget {
         let total_lines = lines.len();
         let available_height = area.height as usize;
         
-        if total_lines > available_height {
-            // Content is larger than area, apply scrolling
-            let max_scroll = total_lines.saturating_sub(available_height);
+        // Always apply scrolling if scroll_offset > 0, even if content fits
+        if scroll_offset > 0 || total_lines > available_height {
+            let max_scroll = if total_lines > available_height {
+                total_lines - available_height
+            } else {
+                total_lines.saturating_sub(1)
+            };
             let effective_scroll = scroll_offset.min(max_scroll);
             
             // Take only the visible portion after scrolling
@@ -535,7 +539,7 @@ impl SystemWidget {
             let paragraph = Paragraph::new(Text::from(visible_lines));
             frame.render_widget(paragraph, area);
         } else {
-            // All content fits, render normally
+            // All content fits and no scroll offset, render normally
             let paragraph = Paragraph::new(Text::from(lines));
             frame.render_widget(paragraph, area);
         }