Move SMART configuration into disk config

- Consolidate SMART thresholds into DiskConfig structure
- Remove separate SmartConfig - disk collector handles all drive data
- Update NixOS configuration to use disk.temperature_* settings
- Remove hardcoded temperature thresholds in disk collector
- Logical grouping: disk collector owns all disk/drive configuration

agent/src/config/mod.rs

@@ -36,7 +36,6 @@ pub struct CollectorConfig {
     pub memory: MemoryConfig,
     pub disk: DiskConfig,
     pub systemd: SystemdConfig,
-    pub smart: SmartConfig,
     pub backup: BackupConfig,
     pub network: NetworkConfig,
     pub nixos: NixOSConfig,
@@ -75,6 +74,11 @@ pub struct DiskConfig {
     pub usage_critical_percent: f32,
     /// Filesystem configurations
     pub filesystems: Vec<FilesystemConfig>,
+    /// SMART monitoring thresholds
+    pub temperature_warning_celsius: f32,
+    pub temperature_critical_celsius: f32,
+    pub wear_warning_percent: f32,
+    pub wear_critical_percent: f32,
 }
 
 /// Filesystem configuration entry
@@ -102,16 +106,6 @@ pub struct SystemdConfig {
     pub host_user_mapping: String,
 }
 
-/// SMART collector configuration
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct SmartConfig {
-    pub enabled: bool,
-    pub interval_seconds: u64,
-    pub temperature_warning_celsius: f32,
-    pub temperature_critical_celsius: f32,
-    pub wear_warning_percent: f32,
-    pub wear_critical_percent: f32,
-}
 
 /// NixOS collector configuration
 #[derive(Debug, Clone, Serialize, Deserialize)]