Fix trigger timing and Variable Names

[captainwerty]

Summary

Fixed timing bug where micros() and millis() were mixed, causing inconsistent trigger behavior.
Now uses millis() + 3000UL for a trigger exactly 3 seconds after setup.

Changes

• Replaced contexspr typo with constexpr
• Changed trigger_time to unsigned long and initialized it properly
• Corrected loop logic for the second motor:

  // fire the 2nd motor & legs once, 3s after setup
  if (!legs_triggered && millis() >= trigger_time) {
      legs_triggered = true;
      triggerMotor();
      triggerLegs();
  }