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

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.20"
+version = "0.1.21"
 edition = "2021"
 
 [dependencies]

dashboard/src/main.rs

@@ -14,7 +14,7 @@ use app::Dashboard;
 
 /// Get hardcoded version
 fn get_version() -> &'static str {
-    "v0.1.20"
+    "v0.1.21"
 }
 
 /// Check if running inside tmux session