Implement WakeOnLAN functionality with simplified configuration

- Add Status::Offline enum variant for disconnected hosts
- All configured hosts now always visible showing offline status when disconnected
- Add WakeOnLAN support using wake-on-lan Rust crate
- Implement w key binding to wake offline hosts with MAC addresses
- Simplify configuration to single [hosts] section with MAC addresses only
- Change critical status icon from ◯ to ! for better visibility
- Add proper MAC address parsing and error handling
- Silent WakeOnLAN operation with logging for success/failure

Configuration format:
[hosts]
hostname = { mac_address = "AA:BB:CC:DD:EE:FF" }

dashboard/src/ui/mod.rs

@@ -9,6 +9,7 @@ use ratatui::{
 use std::collections::HashMap;
 use std::time::Instant;
 use tracing::info;
+use wake_on_lan::MagicPacket;
 
 pub mod theme;
 pub mod widgets;
@@ -93,15 +94,25 @@ pub struct TuiApp {
 
 impl TuiApp {
     pub fn new(config: DashboardConfig) -> Self {
-        Self {
+        let mut app = Self {
             host_widgets: HashMap::new(),
             current_host: None,
-            available_hosts: Vec::new(),
+            available_hosts: config.hosts.keys().cloned().collect(),
             host_index: 0,
             should_quit: false,
             user_navigated_away: false,
             config,
+        };
+        
+        // Sort predefined hosts
+        app.available_hosts.sort();
+        
+        // Initialize with first host if available
+        if !app.available_hosts.is_empty() {
+            app.current_host = Some(app.available_hosts[0].clone());
         }
+        
+        app
     }
 
     /// Get or create host widgets for the given hostname
@@ -186,21 +197,28 @@ impl TuiApp {
     }
 
     /// Update available hosts with localhost prioritization
-    pub fn update_hosts(&mut self, hosts: Vec<String>) {
-        // Sort hosts alphabetically
-        let mut sorted_hosts = hosts.clone();
+    pub fn update_hosts(&mut self, discovered_hosts: Vec<String>) {
+        // Start with configured hosts (always visible)
+        let mut all_hosts: Vec<String> = self.config.hosts.keys().cloned().collect();
+        
+        // Add any discovered hosts that aren't already configured
+        for host in discovered_hosts {
+            if !all_hosts.contains(&host) {
+                all_hosts.push(host);
+            }
+        }
         
         // Keep hosts that have pending transitions even if they're offline
         for (hostname, host_widgets) in &self.host_widgets {
             if !host_widgets.pending_service_transitions.is_empty() {
-                if !sorted_hosts.contains(hostname) {
-                    sorted_hosts.push(hostname.clone());
+                if !all_hosts.contains(hostname) {
+                    all_hosts.push(hostname.clone());
                 }
             }
         }
         
-        sorted_hosts.sort();
-        self.available_hosts = sorted_hosts;
+        all_hosts.sort();
+        self.available_hosts = all_hosts;
         
         // Get the current hostname (localhost) for auto-selection
         let localhost = gethostname::gethostname().to_string_lossy().to_string();
@@ -331,6 +349,33 @@ impl TuiApp {
                         return Ok(Some(UiCommand::TriggerBackup { hostname }));
                     }
                 }
+                KeyCode::Char('w') => {
+                    // Wake on LAN for offline hosts
+                    if let Some(hostname) = self.current_host.clone() {
+                        // Check if host has MAC address configured
+                        if let Some(host_details) = self.config.hosts.get(&hostname) {
+                            if let Some(mac_address) = &host_details.mac_address {
+                                // Parse MAC address and send WoL packet
+                                let mac_bytes = Self::parse_mac_address(mac_address);
+                                match mac_bytes {
+                                    Ok(mac) => {
+                                        match MagicPacket::new(&mac).send() {
+                                            Ok(_) => {
+                                                info!("WakeOnLAN packet sent successfully to {} ({})", hostname, mac_address);
+                                            }
+                                            Err(e) => {
+                                                tracing::error!("Failed to send WakeOnLAN packet to {}: {}", hostname, e);
+                                            }
+                                        }
+                                    }
+                                    Err(_) => {
+                                        tracing::error!("Invalid MAC address format for {}: {}", hostname, mac_address);
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
                 KeyCode::Tab => {
                     // Tab cycles to next host
                     self.navigate_host(1);
@@ -674,7 +719,7 @@ impl TuiApp {
         let metrics = metric_store.get_metrics_for_host(hostname);
 
         if metrics.is_empty() {
-            return Status::Unknown;
+            return Status::Offline;
         }
 
         // First check if we have the aggregated host status summary from the agent
@@ -694,7 +739,8 @@ impl TuiApp {
                 Status::Warning => has_warning = true,
                 Status::Pending => has_pending = true,
                 Status::Ok => ok_count += 1,
-                Status::Unknown => {} // Ignore unknown for aggregation
+                Status::Unknown => {}, // Ignore unknown for aggregation
+                Status::Offline => {}, // Ignore offline for aggregation
             }
         }
 
@@ -735,6 +781,7 @@ impl TuiApp {
         shortcuts.push("s/S: Start/Stop".to_string());
         shortcuts.push("J: Logs".to_string());
         shortcuts.push("L: Custom".to_string());
+        shortcuts.push("w: Wake".to_string());
         
         // Always show quit
         shortcuts.push("q: Quit".to_string());
@@ -773,5 +820,20 @@ impl TuiApp {
         }
     }
 
+    /// Parse MAC address string (e.g., "AA:BB:CC:DD:EE:FF") to [u8; 6]
+    fn parse_mac_address(mac_str: &str) -> Result<[u8; 6], &'static str> {
+        let parts: Vec<&str> = mac_str.split(':').collect();
+        if parts.len() != 6 {
+            return Err("MAC address must have 6 parts separated by colons");
+        }
 
+        let mut mac = [0u8; 6];
+        for (i, part) in parts.iter().enumerate() {
+            match u8::from_str_radix(part, 16) {
+                Ok(byte) => mac[i] = byte,
+                Err(_) => return Err("Invalid hexadecimal byte in MAC address"),
+            }
+        }
+        Ok(mac)
+    }
 }