Merge main, now with the room and creation time index from #295

Both migrations stay; db/schema.rb keeps both indexes and the later version.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0142qgjggdJ2KDdGk7RF9Xm9

db/migrate/20261004225000_add_room_id_and_created_at_index_to_messages.rb

@@ -0,0 +1,5 @@
+class AddRoomIdAndCreatedAtIndexToMessages < ActiveRecord::Migration[8.2]
+  def change
+    add_index :messages, %i[ room_id created_at ]
+  end
+end