feat(event-notifier): improve notification system initialization safety

- Add READY atomic flag to track full initialization status
- Implement initialize_safe and start_safe methods with mutex protection
- Add wait_until_ready function with configurable timeout
- Create initialize_and_start_with_ready_check helper method
- Replace sleep-based waiting with proper readiness checks
- Add safety checks before sending events
- Replace chrono with std::time for time handling
- Update error handling to provide clear initialization status

This change reduces race conditions in multi-threaded environments
and ensures events are only processed when the system is fully ready.

crates/event-notifier/examples/simple.rs

@@ -14,6 +14,7 @@ async fn main() -> Result<(), Box<dyn error::Error>> {
     let mut config = NotificationConfig {
         store_path: "./events".to_string(),
         channel_capacity: 100,
+        timeout: 50,
         adapters: vec![AdapterConfig::Webhook(WebhookConfig {
             endpoint: "http://localhost:8080/webhook".to_string(),
             auth_token: Some("secret-token".to_string()),