Remove hardcoded defaults and migrate dashboard config to NixOS

- Remove all unused configuration options from dashboard config module
- Eliminate hardcoded defaults - dashboard now requires config file like agent
- Keep only actually used config: zmq.subscriber_ports and hosts.predefined_hosts
- Remove unused get_host_metrics function from metric store
- Clean up missing module imports (hosts, utils)
- Make dashboard fail fast if no configuration provided
- Align dashboard config approach with agent configuration pattern

dashboard/src/config/mod.rs

@@ -6,58 +6,19 @@ use std::path::Path;
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct DashboardConfig {
     pub zmq: ZmqConfig,
-    pub ui: UiConfig,
     pub hosts: HostsConfig,
-    pub metrics: MetricsConfig,
-    pub widgets: WidgetsConfig,
 }
 
 /// ZMQ consumer configuration
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ZmqConfig {
     pub subscriber_ports: Vec<u16>,
-    pub connection_timeout_ms: u64,
-    pub reconnect_interval_ms: u64,
-}
-
-/// UI configuration
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct UiConfig {
-    pub refresh_rate_ms: u64,
-    pub theme: String,
-    pub preserve_layout: bool,
 }
 
 /// Hosts configuration
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct HostsConfig {
-    pub auto_discovery: bool,
     pub predefined_hosts: Vec<String>,
-    pub default_host: Option<String>,
-}
-
-/// Metrics configuration
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct MetricsConfig {
-    pub history_retention_hours: u64,
-    pub max_metrics_per_host: usize,
-}
-
-/// Widget configuration
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct WidgetsConfig {
-    pub cpu: WidgetConfig,
-    pub memory: WidgetConfig,
-    pub storage: WidgetConfig,
-    pub services: WidgetConfig,
-    pub backup: WidgetConfig,
-}
-
-/// Individual widget configuration
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct WidgetConfig {
-    pub enabled: bool,
-    pub metrics: Vec<String>,
 }
 
 impl DashboardConfig {
@@ -71,104 +32,18 @@ impl DashboardConfig {
 
 impl Default for DashboardConfig {
     fn default() -> Self {
-        Self {
-            zmq: ZmqConfig::default(),
-            ui: UiConfig::default(),
-            hosts: HostsConfig::default(),
-            metrics: MetricsConfig::default(),
-            widgets: WidgetsConfig::default(),
-        }
+        panic!("Dashboard configuration must be loaded from file - no hardcoded defaults allowed")
     }
 }
 
 impl Default for ZmqConfig {
     fn default() -> Self {
-        Self {
-            subscriber_ports: vec![6130],
-            connection_timeout_ms: 15000,
-            reconnect_interval_ms: 5000,
-        }
-    }
-}
-
-impl Default for UiConfig {
-    fn default() -> Self {
-        Self {
-            refresh_rate_ms: 100,
-            theme: "default".to_string(),
-            preserve_layout: true,
-        }
+        panic!("Dashboard configuration must be loaded from file - no hardcoded defaults allowed")
     }
 }
 
 impl Default for HostsConfig {
     fn default() -> Self {
-        Self {
-            auto_discovery: true,
-            predefined_hosts: vec![
-                "cmbox".to_string(),
-                "labbox".to_string(),
-                "simonbox".to_string(),
-                "steambox".to_string(),
-                "srv01".to_string(),
-                "srv02".to_string(),
-            ],
-            default_host: Some("cmbox".to_string()),
-        }
-    }
-}
-
-impl Default for MetricsConfig {
-    fn default() -> Self {
-        Self {
-            history_retention_hours: 24,
-            max_metrics_per_host: 10000,
-        }
-    }
-}
-
-impl Default for WidgetsConfig {
-    fn default() -> Self {
-        Self {
-            cpu: WidgetConfig {
-                enabled: true,
-                metrics: vec![
-                    "cpu_load_1min".to_string(),
-                    "cpu_load_5min".to_string(),
-                    "cpu_load_15min".to_string(),
-                    "cpu_temperature_celsius".to_string(),
-                ],
-            },
-            memory: WidgetConfig {
-                enabled: true,
-                metrics: vec![
-                    "memory_usage_percent".to_string(),
-                    "memory_total_gb".to_string(),
-                    "memory_available_gb".to_string(),
-                ],
-            },
-            storage: WidgetConfig {
-                enabled: true,
-                metrics: vec![
-                    "disk_nvme0_temperature_celsius".to_string(),
-                    "disk_nvme0_wear_percent".to_string(),
-                    "disk_nvme0_usage_percent".to_string(),
-                ],
-            },
-            services: WidgetConfig {
-                enabled: true,
-                metrics: vec![
-                    "service_ssh_status".to_string(),
-                    "service_ssh_memory_mb".to_string(),
-                ],
-            },
-            backup: WidgetConfig {
-                enabled: true,
-                metrics: vec![
-                    "backup_status".to_string(),
-                    "backup_last_run_timestamp".to_string(),
-                ],
-            },
-        }
+        panic!("Dashboard configuration must be loaded from file - no hardcoded defaults allowed")
     }
 }