Raspberry Pi Pico Button Toggle LED (GP14 + GP2)

Button + LED — next level! 🔁 Unlike #155, no need to hold the button. Press and release → LED on. Press and release again → LED off (toggle). Same circuit as #155 (LED GP14, Button GP2), but big code difference. Learn **edge detection** (capturing the 1→0 falling moment), **state tracking**, **debounce** (mechanical bounce filter). MicroPython's `led.toggle()` swaps state in one line. Foundation of all interactive button projects (mode switcher, IRQ, double-click).