Complete monitoring system restoration

Fully restored CM Dashboard as a complete monitoring system with working
status evaluation and email notifications.

COMPLETED PHASES:
✅ Phase 1: Fixed storage display issues
  - Use lsblk instead of findmnt (eliminates /nix/store bind mount)
  - Fixed NVMe SMART parsing (Temperature: and Percentage Used:)
  - Added sudo to smartctl for permissions
  - Consistent filesystem and tmpfs sorting

✅ Phase 2a: Fixed missing NixOS build information
  - Added build_version field to AgentData
  - NixOS collector now populates build info
  - Dashboard shows actual build instead of "unknown"

✅ Phase 2b: Restored status evaluation system
  - Added status fields to all structured data types
  - CPU: load and temperature status evaluation
  - Memory: usage status evaluation
  - Storage: temperature, health, and filesystem usage status
  - All collectors now use their threshold configurations

✅ Phase 3: Restored notification system
  - Status change detection between collection cycles
  - Email alerts on status degradation (OK→Warning/Critical)
  - Detailed notification content with metric values
  - Full NotificationManager integration

CORE FUNCTIONALITY RESTORED:
- Real-time monitoring with proper status evaluation
- Email notifications on threshold violations
- Correct storage display (nvme0n1 T: 28°C W: 1%)
- Complete status-aware infrastructure monitoring
- Dashboard is now a monitoring system, not just data viewer

The CM Dashboard monitoring system is fully operational.

shared/src/agent_data.rs

@@ -1,10 +1,12 @@
 use serde::{Deserialize, Serialize};
+use crate::Status;
 
 /// Complete structured data from an agent
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AgentData {
     pub hostname: String,
     pub agent_version: String,
+    pub build_version: Option<String>,
     pub timestamp: u64,
     pub system: SystemData,
     pub services: Vec<ServiceData>,
@@ -27,6 +29,8 @@ pub struct CpuData {
     pub load_15min: f32,
     pub frequency_mhz: f32,
     pub temperature_celsius: Option<f32>,
+    pub load_status: Status,
+    pub temperature_status: Status,
 }
 
 /// Memory monitoring data
@@ -39,6 +43,7 @@ pub struct MemoryData {
     pub swap_total_gb: f32,
     pub swap_used_gb: f32,
     pub tmpfs: Vec<TmpfsData>,
+    pub usage_status: Status,
 }
 
 /// Tmpfs filesystem data
@@ -65,6 +70,8 @@ pub struct DriveData {
     pub temperature_celsius: Option<f32>,
     pub wear_percent: Option<f32>,
     pub filesystems: Vec<FilesystemData>,
+    pub temperature_status: Status,
+    pub health_status: Status,
 }
 
 /// Filesystem on a drive
@@ -74,6 +81,7 @@ pub struct FilesystemData {
     pub usage_percent: f32,
     pub used_gb: f32,
     pub total_gb: f32,
+    pub usage_status: Status,
 }
 
 /// Storage pool (MergerFS, RAID, etc.)
@@ -125,6 +133,7 @@ impl AgentData {
         Self {
             hostname,
             agent_version,
+            build_version: None,
             timestamp: chrono::Utc::now().timestamp() as u64,
             system: SystemData {
                 cpu: CpuData {
@@ -133,6 +142,8 @@ impl AgentData {
                     load_15min: 0.0,
                     frequency_mhz: 0.0,
                     temperature_celsius: None,
+                    load_status: Status::Unknown,
+                    temperature_status: Status::Unknown,
                 },
                 memory: MemoryData {
                     usage_percent: 0.0,
@@ -142,6 +153,7 @@ impl AgentData {
                     swap_total_gb: 0.0,
                     swap_used_gb: 0.0,
                     tmpfs: Vec::new(),
+                    usage_status: Status::Unknown,
                 },
                 storage: StorageData {
                     drives: Vec::new(),

shared/src/metrics.rs

@@ -131,6 +131,17 @@ impl HysteresisThresholds {
         }
     }
 
+    /// Evaluate value against thresholds to determine status
+    pub fn evaluate(&self, value: f32) -> Status {
+        if value >= self.critical_high {
+            Status::Critical
+        } else if value >= self.warning_high {
+            Status::Warning
+        } else {
+            Status::Ok
+        }
+    }
+
     pub fn with_custom_gaps(warning_high: f32, warning_gap: f32, critical_high: f32, critical_gap: f32) -> Self {
         Self {
             warning_high,