FEATURE: Configurable auto-bump cooldown (#20507)

Currently the auto-bump cooldown is hard-coded to 24 hours.

This change makes the highlighted 24 hours part configurable (defaulting to 24 hours), and the rest of the process remains the same.

This uses the new CategorySetting model associated with Category. We decided to add this because we want to move away from custom fields due to the lack of type casting and validations, but we want to keep the loading of these optional as they are not needed for almost all of the flows.

Category settings will be back-filled to all categories as part of this change, and creating a new category will now also create a category setting.

config/locales/client.en.yml

@@ -3740,6 +3740,7 @@ en:
       default_slow_mode: 'Enable "Slow Mode" for new topics in this category.'
       parent: "Parent Category"
       num_auto_bump_daily: "Number of open topics to automatically bump daily:"
+      auto_bump_cooldown_days: "Minimum days before bumping the same topic again:"
       navigate_to_first_post_after_read: "Navigate to first post after topics are read"
       notifications:
         title: "change notification level for this category"