Fix type errors: remove unused bcryptRounds, align test with argon2 API

src/lib/auth/password.ts

@@ -19,9 +19,6 @@ function argon2Params() {
 	} as const;
 }
 
-function bcryptRounds(): number {
-	return env.BCRYPT_ROUNDS;
-}
 
 // Which algorithm hashPassword() emits for NEW/upgraded passwords.
 //   - "bcrypt"  (DEFAULT): 60-char $2y$ hash. Fits varchar(255) users.password.