Do I have the right to attend a job interview during paid working hours when I am dismissed?

If you have been dismissed by your employer, you are entitled to reasonable leave with retained salary to visit the employment service or otherwise seek other work. This is stated in Section 14(2) of the Employment Protection Act (LAS). A typical example of when the right to leave exists is precisely as in your case when you are going to a job interview. I would think that what is written in the contract has been taken from this particular legal rule.
This right also applies to fixed-term employees, but only if you have been employed by the employer for more than 12 months in the last three years, and have been told that you will not be extended. You are then entitled to reasonable leave during the last month, for example to attend a job interview, without deduction of pay.
If you are employed on an hourly basis, which is an open-ended part-time contract on an hourly rate schedule, or as a consultant and your contract is terminable, you are also entitled to reasonable time off if you are dismissed.