Wi-Fi controlled light; 230VAC - 12VDC/3.3VDC
You're using a 7812 to make 12V from the DC voltage from the bridge rectifier. You need approximately 2V more than 12V to make that work (officially 1.5 or 1.25 I think, but this is safe to use). That means you need 14V from the bridge rectifier.

When rectifying an AC voltage of \$x\$ volt, you get a DC voltage of \$x\cdot\sqrt2\$ volt. That means you will need an AC voltage of \$14/\sqrt2\approx10V\$. With a 24V AC transformeter, you will get a very high DC voltage, about 34V, much higher than necessary. All the other Volts, 34-14=20, will need to be disippated as heat by the regulator. This is not only a waste of energy, but also may cause issues when the regulator gets overheated. A heatsink is a solution, but a transformator that gives you, say, 12V AC would be better.