Simplify navigation and add vi-style keys

Major UI simplification and navigation improvements:

Changes:
- Removed panel selection concept entirely (no more Shift+Tab)
- Service selection always visible with blue highlighting
- Up/Down arrows now directly control service selection
- Added j/k vi-style navigation keys as alternatives to arrow keys
- Removed panel focus borders - all panels look uniform
- Service commands (s/S) work without panel focus requirements
- Updated keyboard shortcuts to reflect simplified navigation

Navigation:
- Tab: Switch hosts
- ↑↓/jk: Select service (always works)
- R: Rebuild host
- s: Start service
- S: Stop service
- q: Quit

The interface is now much simpler and more intuitive with direct service control.

dashboard/src/ui/theme.rs

@@ -289,18 +289,6 @@ impl Components {
             )
     }
 
-    /// 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 {