Implement comprehensive monitoring improvements

- Add full email notifications with lettre and Stockholm timezone
- Add status persistence to prevent notification spam on restart
- Change nginx monitoring to check backend proxy_pass URLs instead of frontend domains
- Increase nginx site timeout to 10 seconds for backend health checks
- Fix cache intervals: disk (5min), backup (10min), systemd (30s), cpu/memory (5s)
- Remove rate limiting for immediate notifications on all status changes
- Store metric status in /var/lib/cm-dashboard/last-status.json

agent/src/config/defaults.rs

@@ -1,4 +1,4 @@
-// Collection intervals  
+// Collection intervals
 pub const DEFAULT_COLLECTION_INTERVAL_SECONDS: u64 = 2;
 pub const DEFAULT_CPU_INTERVAL_SECONDS: u64 = 5;
 pub const DEFAULT_MEMORY_INTERVAL_SECONDS: u64 = 5;
@@ -46,10 +46,9 @@ pub const DEFAULT_SMART_WEAR_CRITICAL: f32 = 90.0;
 // Backup configuration
 pub const DEFAULT_BACKUP_MAX_AGE_HOURS: u64 = 48;
 
-
 // Notification configuration (from legacy)
 pub const DEFAULT_SMTP_HOST: &str = "localhost";
 pub const DEFAULT_SMTP_PORT: u16 = 25;
 pub const DEFAULT_FROM_EMAIL: &str = "{hostname}@cmtec.se";
 pub const DEFAULT_TO_EMAIL: &str = "cm@cmtec.se";
-pub const DEFAULT_NOTIFICATION_RATE_LIMIT_MINUTES: u64 = 30;
+pub const DEFAULT_NOTIFICATION_RATE_LIMIT_MINUTES: u64 = 0;