refactored auth for JWTs, completed TOTP/2FA implementation, added endpoints to change display name and password

backend/migrations/20260331174422_password-hashing.sql

@@ -0,0 +1,6 @@
+-- Add migration script here
+TRUNCATE TABLE users CASCADE;
+
+ALTER TABLE users DROP COLUMN password;
+ALTER TABLE users ADD COLUMN pass_hash VARCHAR(255) NOT NULL;
+ALTER TABLE users ADD CONSTRAINT users_username_unique UNIQUE (username);