feat: add country input to city form

- Added country input field to the city form for better user experience.
- Removed unused region and weather-related fields to declutter the form.

This change improves the data captured for cities and enhances the form's usability by focusing on relevant information.

app/admin/cities.rb

@@ -41,13 +41,11 @@ ActiveAdmin.register City do
     f.inputs do
       f.input :active
       f.input :name
+      f.input :country
       f.input :latitude
       f.input :longitude
       f.input :priority
       f.input :timezone
-      f.input :region
-      f.input :last_weather_fetch
-      f.input :last_image_generation
     end
     f.actions
   end