Clean up code

Clean up warnings on newer Rust versions. Drop some no-longer used
tables and columns

migrations/20260516170852_drop_columns.sql

@@ -0,0 +1,17 @@
+SET foreign_key_checks = 0;
+
+-- Drop all old tables
+DROP TABLE IF EXISTS users_old;
+DROP TABLE IF EXISTS messages;
+DROP TABLE IF EXISTS embeds;
+DROP TABLE IF EXISTS embed_fields;
+DROP TABLE IF EXISTS command_aliases;
+DROP TABLE IF EXISTS macro;
+DROP TABLE IF EXISTS roles;
+DROP TABLE IF EXISTS command_restrictions;
+
+-- Drop columns from channels that are no longer used
+ALTER TABLE channels DROP COLUMN `name`;
+ALTER TABLE channels DROP COLUMN `blacklisted`;
+
+SET foreign_key_checks = 1;