Implement complete keyboard navigation and UI enhancement

Phase 1 - Panel Navigation:
- Add PanelType enum and panel focus state management
- Implement Shift+Tab cycling between panels (System → Services → Backup → Network)
- Add visual focus indicators with blue borders for focused panels
- Preserve existing Tab behavior for host switching

Phase 2 - Dynamic Statusbar:
- Add bottom statusbar with context-aware shortcuts
- Display different shortcuts based on focused panel
- Global shortcuts: Tab, Shift+Tab, Up/Down arrows, Q
- Panel-specific shortcuts: R (Rebuild), Space/R (Services), B (Backup), N (Network)

Phase 3 - Scrolling Support:
- Add scroll state management per host and panel type
- Implement Up/Down arrow key scrolling within focused panels
- Smart scrolling that activates only when content exceeds panel height
- Scroll bounds checking to prevent over-scrolling

Complete keyboard navigation experience with visual feedback and contextual help.

dashboard/src/ui/theme.rs

@@ -292,6 +292,19 @@ impl Components {
                     .bg(Theme::background()),
             )
     }
+
+    /// Widget block with focus indicator (blue border)
+    pub fn focused_widget_block(title: &str) -> Block<'_> {
+        Block::default()
+            .title(title)
+            .borders(Borders::ALL)
+            .style(Style::default().fg(Theme::highlight()).bg(Theme::background())) // Blue border for focus
+            .title_style(
+                Style::default()
+                    .fg(Theme::highlight()) // Blue title for focus
+                    .bg(Theme::background()),
+            )
+    }
 }
 
 impl Typography {