Use more accurate beginning/ending times in annual report source (#31751)

app/lib/annual_report/source.rb

@@ -11,6 +11,16 @@ class AnnualReport::Source
   protected
 
   def year_as_snowflake_range
-    (Mastodon::Snowflake.id_at(DateTime.new(year, 1, 1))..Mastodon::Snowflake.id_at(DateTime.new(year, 12, 31)))
+    (beginning_snowflake_id..ending_snowflake_id)
+  end
+
+  private
+
+  def beginning_snowflake_id
+    Mastodon::Snowflake.id_at DateTime.new(year).beginning_of_year
+  end
+
+  def ending_snowflake_id
+    Mastodon::Snowflake.id_at DateTime.new(year).end_of_year
   end
 end