Update to v0.1.19 with event-driven status aggregation

Major architectural improvements:

CORE CHANGES:
- Remove notification_interval_seconds - status aggregation now immediate
- Status calculation moved to collection phase instead of transmission
- Event-driven transmission triggers immediately on status changes
- Dual transmission strategy: immediate on change + periodic backup
- Real-time notifications without batching delays

TECHNICAL IMPROVEMENTS:
- process_metric() now returns bool indicating status change
- Immediate ZMQ broadcast when status changes detected
- Status aggregation happens during metric collection, not later
- Legacy get_nixos_build_info() method removed (unused)
- All compilation warnings fixed

BEHAVIOR CHANGES:
- Critical alerts sent instantly instead of waiting for intervals
- Dashboard receives real-time status updates
- Notifications triggered immediately on status transitions
- Backup periodic transmission every 1s ensures heartbeat

This provides much more responsive monitoring with instant alerting
while maintaining the reliability of periodic transmission as backup.

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.18"
+version = "0.1.19"
 edition = "2021"
 
 [dependencies]

dashboard/src/main.rs

@@ -14,7 +14,7 @@ use app::Dashboard;
 
 /// Get hardcoded version
 fn get_version() -> &'static str {
-    "v0.1.18"
+    "v0.1.19"
 }
 
 /// Check if running inside tmux session