feat: implement flash messages system with auto-dismiss notifications

- Add flash message helper and styles for consistent notifications
- Replace Devise error messages with flash-based notifications
- Add dashboard page with event statistics
- Configure SMTP settings for development and production
- Update authentication controllers to use flash messages
- Add JavaScript controller for auto-dismiss functionality

app/javascript/controllers/index.js

@@ -5,9 +5,12 @@
 import { application } from "./application"
 
 import LogoutController from "./logout_controller"
-import ShadcnTestController from "./shadcn_test_controller"
+import FlashMessage from "./flash_message_controller"
 import CounterController from "./counter_controller"
+import ShadcnTestController from "./shadcn_test_controller"
 
-application.register("logout", LogoutController)
-application.register("shadcn-test", ShadcnTestController)
-application.register("counter", CounterController)
+application.register("logout", LogoutController) // Allow logout using js
+application.register("flash-message", FlashMessage) // Dismiss notification after 5 secondes
+application.register("counter", CounterController) // Simple counter for homepage
+
+application.register("shadcn-test", ShadcnTestController) // Test controller for Shadcn