feat: add broadcast session tracking and chatlog service with database migrations

broadcasters/migrations/5_chatlog_room_text.up.sql

@@ -0,0 +1,4 @@
+-- 5_chatlog_room_text.up.sql
+-- Modifica la colonna "room" da UUID a TEXT per supportare qualsiasi identificatore di stanza (es. nomi LiveKit, slug, broadcast-uuid).
+
+ALTER TABLE chatlog ALTER COLUMN room TYPE TEXT;