Suggest input capcitor of regulator higher than output capacitor as it store energy after rectifier. 1000uF input and 100uF output capacitor.
Add high frequency 100nF decoupling capacitors to input and output of regulator, place closely to regulator as posible to reduce ringing/ output ripple.
Add 100nF decoupling capacitor to Vcc & GND of MCU, place closely to MCUas posible to reduce radiate EMI.
All unused GPIO should connect to GND, don't floating them.
Should sense directly AC zero crossing instead through transformer.
All net from GPIO of MCU should be short as possible.
Add damping capacitor to zero detect pin to ignore noise when motor run, suggest < 1nF, place closely to GPIO in as posible.
Add TVS or R, or Inductor before input capacitor of regulator to reduce spike from AC source. Regulator can't not clamp fast trasient/surge voltage.
Add damping capacitor for button < 100nF.
Should have indepent watchdog to reset if MCU hang, or on/off switch to reset MCU.
Layout should have large clearance for isolation and between low&high voltage.
Reliability has some levels. Your design is not prefer for higher level because it is too simple. It has no input & output current protection, when start motor the start current quite high, it can damage triac. So, the firmware need to increase slowly on duty instead of open full. When output short circuit, it will bloom .... Your circuit must have at least one fuse for input. Better when implement 02 fuses, if output short to Earth.