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/unlocks/new.html.erb

@@ -1,7 +1,6 @@
 <h2>Resend unlock instructions</h2>
 
 <%= form_for(resource, as: resource_name, url: unlock_path(resource_name), html: { method: :post }) do |f| %>
-  <%= render "devise/shared/error_messages", resource: resource %>
 
   <div class="field">
     <%= f.label :email %><br />