posts: automatically tag videos with sound.

Automatically add the `sound` tag if the post has sound. Remove the tag if the post doesn't have sound.

A video is considered to have sound if its peak loudness is greater than -70 dB. The current quietest post
on Danbooru has a peak loudness of -62 dB (post #3470668), but it's possible to have audible sound at
-80 dB or possibly even lower. It's hard to draw a clear line between "silent" and "barely audible".

app/models/media_asset.rb

@@ -22,7 +22,7 @@ class MediaAsset < ApplicationRecord
   has_many :ai_tags
 
   delegate :frame_delays, :metadata, to: :media_metadata
-  delegate :is_non_repeating_animation?, :is_greyscale?, :is_rotated?, :is_ai_generated?, to: :metadata
+  delegate :is_non_repeating_animation?, :is_greyscale?, :is_rotated?, :is_ai_generated?, :has_sound?, to: :metadata
 
   scope :public_only, -> { where(is_public: true) }
   scope :private_only, -> { where(is_public: false) }