Update version to 0.1.21 and fix dashboard data caching

- Separate dashboard updates from email notifications for immediate status aggregation
- Add metric caching to MetricCollectionManager for instant dashboard updates
- Dashboard now receives cached data every 1 second instead of waiting for collection intervals
- Fix transmission to use cached metrics rather than triggering fresh collection
- Email notifications maintain separate 60-second batching interval
- Update configurable email notification aggregation interval

agent/src/metrics/mod.rs

@@ -21,6 +21,7 @@ struct TimedCollector {
 pub struct MetricCollectionManager {
     collectors: Vec<TimedCollector>,
     status_tracker: StatusTracker,
+    cached_metrics: Vec<Metric>,
 }
 
 impl MetricCollectionManager {
@@ -177,6 +178,7 @@ impl MetricCollectionManager {
         Ok(Self {
             collectors,
             status_tracker: StatusTracker::new(),
+            cached_metrics: Vec::new(),
         })
     }
 
@@ -198,6 +200,9 @@ impl MetricCollectionManager {
                 }
             }
         }
+        
+        // Cache the collected metrics
+        self.cached_metrics = all_metrics.clone();
         Ok(all_metrics)
     }
 
@@ -231,6 +236,18 @@ impl MetricCollectionManager {
                 }
             }
         }
+        
+        // Update cache with newly collected metrics
+        if !all_metrics.is_empty() {
+            // Merge new metrics with cached metrics (replace by name)
+            for new_metric in &all_metrics {
+                // Remove any existing metric with the same name
+                self.cached_metrics.retain(|cached| cached.name != new_metric.name);
+                // Add the new metric
+                self.cached_metrics.push(new_metric.clone());
+            }
+        }
+        
         Ok(all_metrics)
     }
 
@@ -238,5 +255,10 @@ impl MetricCollectionManager {
     pub async fn collect_all_metrics(&mut self) -> Result<Vec<Metric>> {
         self.collect_metrics_timed().await
     }
+    
+    /// Get cached metrics without triggering fresh collection
+    pub fn get_cached_metrics(&self) -> Vec<Metric> {
+        self.cached_metrics.clone()
+    }
 
 }