feat: add logging and refactor image attachment

- Add logging to track the generation of weather art for each city.
- Refactor image attachment process to streamline the code by removing the
  separate method for attaching images.
- Ensure proper handling of the temporary file used for image processing.

These changes improve observability during the weather art generation
process and encapsulate the image attachment logic within the primary
method, reducing the overhead of a method call. The adjustments also
ensure that temporary files are managed correctly to prevent resource
leaks.

app/workers/batch_generate_weather_arts_worker.rb

@@ -12,6 +12,7 @@ class BatchGenerateWeatherArtsWorker
 
     cities_to_process.each do |city|
       break if Time.current - start_time > MAX_DURATION
+      Rails.logger.info "Generating weather art for #{city.name}"
 
       GenerateWeatherArtWorker.perform_async(city.id)
       sleep SLEEP_DURATION

app/workers/generate_weather_art_worker.rb

@@ -36,6 +36,8 @@ class GenerateWeatherArtWorker
   end
 
   def create_weather_art(weather_data, prompt, image_url)
+    tempfile = nil
+
     ActiveRecord::Base.transaction do
       weather_art = city.weather_arts.create!(
         weather_date: Date.today,
@@ -43,21 +45,21 @@ class GenerateWeatherArtWorker
         **weather_data
       )
 
-      attach_image(weather_art, image_url)
+      tempfile = Down.download(image_url)
+
+      weather_art.image.attach(
+        io: File.open(tempfile.path),
+        filename: generate_filename,
+        content_type: 'image/png'
+      )
+
       weather_art
     end
-  end
-
-  def attach_image(weather_art, image_url)
-    tempfile = Down.download(image_url)
-    weather_art.image.attach(
-      io: tempfile,
-      filename: generate_filename,
-      content_type: "image/png"
-    )
   ensure
-    tempfile&.close
-    tempfile&.unlink
+    if tempfile
+      tempfile.close
+      tempfile.unlink
+    end
   end
 
   def generate_filename