Implement per-host widget cache for instant host switching

Resolves widget data persistence issue where switching hosts left stale data
from the previous host displayed in widgets.

Key improvements:
- Add Clone derives to all widget structs (CpuWidget, MemoryWidget,
  ServicesWidget, BackupWidget)
- Create HostWidgets struct to cache widget states per hostname
- Update TuiApp with HashMap<String, HostWidgets> for per-host storage
- Fix borrowing issues by cloning hostname before mutable self borrow
- Implement instant widget state restoration when switching hosts

Tab key host switching now displays cached widget data for each host
without stale information persistence between switches.

dashboard/src/ui/mod.rs

@@ -6,6 +6,7 @@ use ratatui::{
     widgets::{Block, Paragraph},
     Frame,
 };
+use std::collections::HashMap;
 use std::time::Instant;
 use tracing::info;
 
@@ -17,24 +18,43 @@ use crate::metrics::{MetricStore, WidgetType};
 use cm_dashboard_shared::{Metric, Status};
 use theme::{Theme, Layout as ThemeLayout, Typography, Components, StatusIcons};
 
+/// Widget states for a specific host
+#[derive(Clone)]
+pub struct HostWidgets {
+    /// CPU widget state
+    pub cpu_widget: CpuWidget,
+    /// Memory widget state  
+    pub memory_widget: MemoryWidget,
+    /// Services widget state
+    pub services_widget: ServicesWidget,
+    /// Backup widget state
+    pub backup_widget: BackupWidget,
+    /// Last update time for this host
+    pub last_update: Option<Instant>,
+}
+
+impl HostWidgets {
+    pub fn new() -> Self {
+        Self {
+            cpu_widget: CpuWidget::new(),
+            memory_widget: MemoryWidget::new(),
+            services_widget: ServicesWidget::new(),
+            backup_widget: BackupWidget::new(),
+            last_update: None,
+        }
+    }
+}
+
 /// Main TUI application
 pub struct TuiApp {
-    /// CPU widget
-    cpu_widget: CpuWidget,
-    /// Memory widget
-    memory_widget: MemoryWidget,
-    /// Services widget
-    services_widget: ServicesWidget,
-    /// Backup widget
-    backup_widget: BackupWidget,
+    /// Widget states per host (hostname -> HostWidgets)
+    host_widgets: HashMap<String, HostWidgets>,
     /// Current active host
     current_host: Option<String>,
     /// Available hosts
     available_hosts: Vec<String>,
     /// Host index for navigation
     host_index: usize,
-    /// Last update time
-    last_update: Option<Instant>,
     /// Should quit application
     should_quit: bool,
 }
@@ -42,45 +62,44 @@ pub struct TuiApp {
 impl TuiApp {
     pub fn new() -> Self {
         Self {
-            cpu_widget: CpuWidget::new(),
-            memory_widget: MemoryWidget::new(),
-            services_widget: ServicesWidget::new(),
-            backup_widget: BackupWidget::new(),
+            host_widgets: HashMap::new(),
             current_host: None,
             available_hosts: Vec::new(),
             host_index: 0,
-            last_update: None,
             should_quit: false,
         }
     }
     
+    /// Get or create host widgets for the given hostname
+    fn get_or_create_host_widgets(&mut self, hostname: &str) -> &mut HostWidgets {
+        self.host_widgets.entry(hostname.to_string()).or_insert_with(HostWidgets::new)
+    }
+    
     /// Update widgets with metrics from store
     pub fn update_metrics(&mut self, metric_store: &MetricStore) {
-        if let Some(ref hostname) = self.current_host {
-            // Update CPU widget
-            let cpu_metrics = metric_store.get_metrics_for_widget(hostname, WidgetType::Cpu);
-            self.cpu_widget.update_from_metrics(&cpu_metrics);
-            
-            // Update Memory widget
-            let memory_metrics = metric_store.get_metrics_for_widget(hostname, WidgetType::Memory);
-            self.memory_widget.update_from_metrics(&memory_metrics);
-            
-            // Update Services widget - get all metrics that start with "service_"
-            let all_metrics = metric_store.get_metrics_for_host(hostname);
+        if let Some(hostname) = self.current_host.clone() {
+            // Get metrics first while hostname is borrowed
+            let cpu_metrics = metric_store.get_metrics_for_widget(&hostname, WidgetType::Cpu);
+            let memory_metrics = metric_store.get_metrics_for_widget(&hostname, WidgetType::Memory);
+            let all_metrics = metric_store.get_metrics_for_host(&hostname);
             let service_metrics: Vec<&Metric> = all_metrics.iter()
                 .filter(|m| m.name.starts_with("service_"))
                 .copied()
                 .collect();
-            self.services_widget.update_from_metrics(&service_metrics);
-            
-            // Update Backup widget - get all metrics that start with "backup_"
             let all_backup_metrics: Vec<&Metric> = all_metrics.iter()
                 .filter(|m| m.name.starts_with("backup_"))
                 .copied()
                 .collect();
-            self.backup_widget.update_from_metrics(&all_backup_metrics);
             
-            self.last_update = Some(Instant::now());
+            // Now get host widgets and update them
+            let host_widgets = self.get_or_create_host_widgets(&hostname);
+            
+            host_widgets.cpu_widget.update_from_metrics(&cpu_metrics);
+            host_widgets.memory_widget.update_from_metrics(&memory_metrics);
+            host_widgets.services_widget.update_from_metrics(&service_metrics);
+            host_widgets.backup_widget.update_from_metrics(&all_backup_metrics);
+            
+            host_widgets.last_update = Some(Instant::now());
         }
     }
     
@@ -184,7 +203,12 @@ impl TuiApp {
         // Render new panel layout
         self.render_system_panel(frame, left_chunks[0], metric_store);
         self.render_backup_panel(frame, left_chunks[1]);
-        self.services_widget.render(frame, content_chunks[1]);  // Services takes full right side
+        
+        // Render services widget for current host
+        if let Some(hostname) = self.current_host.clone() {
+            let host_widgets = self.get_or_create_host_widgets(&hostname);
+            host_widgets.services_widget.render(frame, content_chunks[1]);  // Services takes full right side
+        }
     }
     
     /// Render btop-style minimal title
@@ -241,8 +265,12 @@ impl TuiApp {
             ])
             .split(inner_area);
         
-        self.cpu_widget.render(frame, content_chunks[0]);
-        self.memory_widget.render(frame, content_chunks[1]);
+        // Get current host widgets, create if none exist
+        if let Some(hostname) = self.current_host.clone() {
+            let host_widgets = self.get_or_create_host_widgets(&hostname);
+            host_widgets.cpu_widget.render(frame, content_chunks[0]);
+            host_widgets.memory_widget.render(frame, content_chunks[1]);
+        }
         self.render_storage_section(frame, content_chunks[2], metric_store);
     }
     
@@ -250,7 +278,12 @@ impl TuiApp {
         let backup_block = Components::widget_block("backup");
         let inner_area = backup_block.inner(area);
         frame.render_widget(backup_block, area);
-        self.backup_widget.render(frame, inner_area);
+        
+        // Get current host widgets for backup widget
+        if let Some(hostname) = self.current_host.clone() {
+            let host_widgets = self.get_or_create_host_widgets(&hostname);
+            host_widgets.backup_widget.render(frame, inner_area);
+        }
     }
     
     

dashboard/src/ui/widgets/backup.rs

@@ -10,6 +10,7 @@ use super::Widget;
 use crate::ui::theme::{Theme, Typography, Components, StatusIcons};
 
 /// Backup widget displaying backup status, services, and repository information
+#[derive(Clone)]
 pub struct BackupWidget {
     /// Overall backup status
     overall_status: Status,

dashboard/src/ui/widgets/cpu.rs

@@ -10,6 +10,7 @@ use super::Widget;
 use crate::ui::theme::{Theme, Typography, Components, StatusIcons};
 
 /// CPU widget displaying load, temperature, and frequency
+#[derive(Clone)]
 pub struct CpuWidget {
     /// CPU load averages (1, 5, 15 minutes)
     load_1min: Option<f32>,

dashboard/src/ui/widgets/memory.rs

@@ -10,6 +10,7 @@ use super::Widget;
 use crate::ui::theme::{Theme, Typography, Components, StatusIcons};
 
 /// Memory widget displaying usage, totals, and swap information
+#[derive(Clone)]
 pub struct MemoryWidget {
     /// Memory usage percentage
     usage_percent: Option<f32>,

dashboard/src/ui/widgets/services.rs

@@ -12,6 +12,7 @@ use crate::ui::theme::{Theme, Typography, Components, StatusIcons};
 use ratatui::style::Style;
 
 /// Services widget displaying hierarchical systemd service statuses
+#[derive(Clone)]
 pub struct ServicesWidget {
     /// Parent services (nginx, docker, etc.)
     parent_services: HashMap<String, ServiceInfo>,