Implement hysteresis for metric status changes to prevent flapping

Add comprehensive hysteresis support to prevent status oscillation near
threshold boundaries while maintaining responsive alerting.

Key Features:
- HysteresisThresholds with configurable upper/lower limits
- StatusTracker for per-metric status history
- Default gaps: CPU load 10%, memory 5%, disk temp 5°C

Updated Components:
- CPU load collector (5-minute average with hysteresis)
- Memory usage collector (percentage-based thresholds)
- Disk temperature collector (SMART data monitoring)
- All collectors updated to support StatusTracker interface

Cache Interval Adjustments:
- Service status: 60s → 10s (faster response)
- Disk usage: 300s → 60s (more frequent checks)
- Backup status: 900s → 60s (quicker updates)
- SMART data: moved to 600s tier (10 minutes)

Architecture:
- Individual metric status calculation in collectors
- Centralized StatusTracker in MetricCollectionManager
- Status aggregation preserved in dashboard widgets

agent/src/collectors/systemd.rs

@@ -1,6 +1,6 @@
 use anyhow::Result;
 use async_trait::async_trait;
-use cm_dashboard_shared::{Metric, MetricValue, Status};
+use cm_dashboard_shared::{Metric, MetricValue, Status, StatusTracker};
 use std::process::Command;
 use std::sync::RwLock;
 use std::time::Instant;
@@ -401,7 +401,7 @@ impl Collector for SystemdCollector {
         "systemd"
     }
 
-    async fn collect(&self) -> Result<Vec<Metric>, CollectorError> {
+    async fn collect(&self, _status_tracker: &mut StatusTracker) -> Result<Vec<Metric>, CollectorError> {
         let start_time = Instant::now();
         debug!("Collecting systemd services metrics");