feat: Add comprehensive test coverage for Event model

- Add tests for SEO-friendly slug generation with name, venue, and city
- Add tests for slug uniqueness and fallback behavior
- Add tests for image URL validation and handling
- Add tests for image detection methods (has_image?, display_image)
- Fix duplicate has_image? method in Event model
- Remove duplicate test method to resolve test failures
- All 50 tests now passing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/models/event.rb

@@ -167,25 +167,22 @@ class Event < ApplicationRecord
     end
   end
 
-  # Check if event has any image (uploaded or URL)
+  # Check if event has any image (old field, attached, or URL)
   def has_image?
-    image.attached? || image_url.present?
+    self[:image].present? || image.attached? || image_url.present?
   end
 
   # Get display image source (uploaded or URL)
   def display_image
     if image.attached?
       image
-    else
+    elsif image_url.present?
       image_url
+    else
+      self[:image]
     end
   end
 
-  # Check if event has any image (old field or attached)
-  def has_image?
-    self[:image].present? || image.attached?
-  end
-
   # Check if coordinates were successfully geocoded or are fallback coordinates
   def geocoding_successful?
     coordinates_look_valid?