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/flash_message_controller.js

@@ -0,0 +1,27 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static targets = ["message"]
+
+  connect() {
+    console.log("FlashMessageController mounted", this.element);
+
+    // Auto-dismiss after 5 seconds
+    this.timeout = setTimeout(() => {
+      this.close()
+    }, 5000)
+  }
+
+  disconnect() {
+    if (this.timeout) {
+      clearTimeout(this.timeout)
+    }
+  }
+
+  close() {
+    this.element.classList.add('opacity-0', 'transition-opacity', 'duration-300')
+    setTimeout(() => {
+      this.element.remove()
+    }, 300)
+  }
+}