Is the intention (niyyah) obligatory for discharging zakat on my behalf when my father paid it for me without my knowledge, and what are the implications of that?

Zakat on a minor's wealth is obligatory according to the majority of scholars if the wealth reaches the nisab (minimum threshold) and a hawl (lunar year) passes over it, and the guardian is responsible for its disbursement. What your father did by paying the zakat on your wealth was correct, and your knowledge or intention is not required for this, because the guardian acts on behalf of the minor. After reaching puberty, your father cannot pay zakat on your behalf without your permission. If you were unable to dispose of the money until you reached eighteen years of age, then zakat is obligatory for one year upon its receipt. However, if the money remained under your father's control and he did not gift it to you until you reached the aforementioned age, then there is no zakat due on it until a hawl passes while it is in your possession. If the money is in an interest-based bank, it must be withdrawn and invested in an Islamic bank, and the usurious interest must be disposed of by giving it to the poor or for the benefit of Muslims.