Set snowflake IDs for backdated statuses (#5260)

- Rename Mastodon::TimestampIds into Mastodon::Snowflake for clarity
- Skip for statuses coming from inbox, aka delivered in real-time
- Skip for statuses that claim to be from the future

app/models/status.rb

@@ -136,6 +136,8 @@ class Status < ApplicationRecord
 
   after_create :store_uri, if: :local?
 
+  around_create Mastodon::Snowflake::Callbacks
+
   before_validation :prepare_contents, if: :local?
   before_validation :set_reblog
   before_validation :set_visibility