feat: optimize batch weather art generation

- Introduce BATCH_SIZE constant to limit processed cities
- Shuffle and limit eligible cities processing to enhance worker efficiency

This update improves the performance of the BatchGenerateWeatherArtsWorker
by ensuring that only a set number of cities are processed within the
allotted time, reducing the risk of timeouts and making the overall
system more responsive.

app/workers/batch_generate_weather_arts_worker.rb

@@ -1,19 +1,16 @@
 class BatchGenerateWeatherArtsWorker
   include Sidekiq::Worker
-
   GENERATION_INTERVAL = 24.hours
   MAX_DURATION = 50.minutes
   SLEEP_DURATION = 120.seconds
+  BATCH_SIZE = 20
 
   def perform(*args)
     start_time = Time.current
-
-    cities_to_process = get_eligible_cities
-
+    cities_to_process = get_eligible_cities.shuffle.take(BATCH_SIZE)
     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
     end
@@ -23,7 +20,6 @@ class BatchGenerateWeatherArtsWorker
 
   def get_eligible_cities
     cutoff_time = Time.current - GENERATION_INTERVAL
-
     City.active
         .joins("LEFT JOIN (
           SELECT city_id, MAX(created_at) as last_generation_time