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/views/devise/shared/_error_messages.html.erb

@@ -1,14 +1,5 @@
 <% if resource.errors.any? %>
-  <div id="error_explanation" data-turbo-cache="false" class="bg-red-50 border border-red-200 rounded-md p-4 mb-4">
-    <h2 class="text-lg font-medium text-red-800 mb-3">
-      <%= I18n.t("errors.messages.not_saved",
-                 count: resource.errors.count,
-                 resource: resource.class.model_name.human.downcase) %>
-    </h2>
-    <ul class="list-disc list-inside space-y-1">
-      <% resource.errors.full_messages.each do |message| %>
-        <li class="text-sm text-red-700"><%= message %></li>
-      <% end %>
-    </ul>
-  </div>
+  <% resource.errors.full_messages.each do |message| %>
+    <% flash.now[:error] = message %>
+  <% end %>
 <% end %>